Log in to get started!

Don't have an account yet? You can create one below.

Student Instructor
Display Title
Korean War in 1950

Set in September 1950. Five years after the conclusion of World War II, the Korean Peninsula is under threat of falling to a Soviet-supported, communist regime.


It is late summer 1950, and the United States is at war on the Korean Peninsula. Just a few months earlier, the Soviet-backed Democratic People’s Republic of Korea (North Korea) invaded the U.S.-supported Republic of Korea (South Korea), making significant territorial gains and pushing U.S.-led UN forces to the southern tip of the peninsula. Plans are in place for a landing near the border with North Korea, which, if successful, will swiftly liberate South Korea. President Harry Truman is now faced with a fundamental question: should U.S. forces simply restore the status prior to the war, pushing North Korea’s military back beyond its own border, or should the United States push on and try to unify the peninsula under a single, democratic government?

Lead Image
Soldiers in Korean War.

The Situation

At the conclusion of World War II, Korea—formerly under Japanese control—was divided at the thirty-eighth parallel into a U.S.-occupied south and a Soviet-occupied north. Although the division was meant to be temporary, by 1948 both countries had declared independence. North Korea became a Soviet-supported communist state; South Korea was supported by the United States. Two years later, North Korea invaded South Korea in an attempt to bring the entire peninsula under its control. After several weeks of fighting, U.S. and South Korean forces were defending against North Korea’s southward advance an area called the Pusan perimeter, in the southernmost portion of the peninsula. General Douglas MacArthur, who was commanding U.S. and allied forces as part of a UN mission, was also making plans for a landing at Inchon, near the South Korean capital of Seoul, in order to surprise North Korean troops and recapture Seoul.  

Anticipating the possible success of the Inchon landing, President Truman has convened National Security Council members to advise him on whether to extend the U.S. military intervention north of the thirty-eighth parallel in an attempt to unify the Korean Peninsula. As the dividing lines of the emerging Cold War start to solidify, the United States will have to weigh whether intervention in North Korea is worth a potential  conflict with another great power.




  • U.S. support for democratic governance
  • Costs, benefits, and risks of military interventions
  • U.S. interests in East Asia
  • The UN Security Council and the U.S. role at the United Nations
  • Early flash points in the Cold War
  • Security and diplomacy in Northeast Asia
  • Chinese and Soviet support of North Korea
Guide Sections
An Introduction to the National Security Council
National Security Council meeting

“The function of the Council shall be to advise the President with respect to the integration of domestic, foreign, and military policies relating to the national security...”

—Title I of the National Security Act of 1947

1.1 Overview 

The United States plays a critical role in establishing and maintaining international order in an increasingly globalized world. The range of foreign policy issues that require its attention or involvement is vast. From conflicts in Afghanistan, Iraq, and Syria to tensions with North Korea and Iran; from longstanding alliances with European and Asian powers to complex, evolving relationships with Brazil, China, India, Russia, and South Africa; from the stability of global finance to the promotion of economic opportunity in low-income countries; from climate to health to nuclear proliferation to terrorism—there is little around the world in which the United States does not have a vested interest. Furthermore, issues such as immigration, trade, and cybersecurity underscore the fading distinction between domestic and international matters.

U.S. leaders use a range of tools to pursue a foreign policy that they believe will protect national security and achieve U.S. goals. These tools include:

  • diplomatic tools, such as bilateral or multilateral consultations and negotiations, treaties, defense and security agreements, resolutions in global and regional bodies such as the United Nations (UN), and public diplomacy to promote U.S. views and culture;
  • economic tools, such as trade and investment agreements, tariffs, sanctions, embargoes and boycotts, bilateral and multilateral development assistance, loans for the purchase of U.S. exports, and sales of arms, equipment, and technology;
  • military tools, such as missile strikes by manned or unmanned vehicles, nuclear deterrence, ground force deployments, ship and submarine patrols, blockades, unilateral or partnered military exercises, foreign military training, and special operations forces;
  • unconventional tools, which are actions, sometimes secret, taken by the U.S. government and its proxies, such as training and assisting foreign intelligence services, supporting armed nonstate actors, private security contracting, and cyberwarfare.

Effective policymaking and policy implementation require the deft use of different combinations of these tools, depending on the circumstances. To accomplish this, policymakers must clearly define U.S. interests and gauge the interests, resources, and motivations of foreign governments and nonstate actors. The U.S. intelligence community helps policymakers in their work by collecting and analyzing a vast range of information, including satellite images, communications records, documents, data, and personal observations.

Foreign policy successes and failures are often associated with decisions made by presidents. Less explored is the decision-making apparatus that helps the president make those critical choices and coordinate their implementation. This guide will help you understand the system through which the United States creates and implements its foreign policy.

National Security Council meeting
CIA Director George Bush discusses the evacuation of Americans from Beirut

“....I envisioned a special role for the national security advisor, who is the manager of the National Security Council. I needed an honest broker who would objectively present to the president the views of the various cabinet officers across the spectrum.”

— George H.W. Bush, “A World Transformed,” p. 18

1.2 The Interagency Process

Whether it aims to respond to an immediate crisis or to advance a long-term objective, a successful foreign policy–making process starts with a clear articulation of interests and goals. Policymakers and their advisors then formulate policy options to meet those goals and consider each option’s strengths and weaknesses. This process is challenging in the best of times. Information may be unreliable or incomplete, an adversary’s intentions may be unclear, and a decision’s consequences may be unknowable. Leaders often have to choose from a list on which every option is imperfect. Adding to this uncertainty is the complexity of the U.S. government’s foreign policy machinery: numerous agencies—each with its own interests and biases—seek to influence how policy is decided and carried out. In these circumstances, it takes considerable effort to run a process capable of producing sound policy decisions.

The National Security Council (NSC) plays a critical role in this effort. Its mission is to help the president effectively use a variety of instruments—military, diplomatic, or otherwise—to forge policies that advance U.S. national security goals.

The NSC was created by the National Security Act of 1947, which defined it as an interagency body intended to “advise the president with respect to the integration of domestic, foreign, and military policies relating to the national security.” Following World War II, in an age of expanded American interests and responsibilities, the NSC was expected to provide a place where the heads of federal departments and agencies could cooperate to develop and recommend to the president policies that would advance U.S. aims. The NSC and its staff were also meant to manage the policymaking process so that the president would receive a full range of advice and opinion from the departments and agencies involved in national security.

The NSC has evolved significantly over the years, adapting to the preferences of successive presidents and the challenges they faced. Variables such NSC meeting attendees, the frequency of meetings, the amount and format of information passed to the president, the importance of consensus, and the relative dominance of the NSC over other government institutions have changed over the decades.

During this time, the NSC has evolved to comprise various interagency committees and a large staff to prepare analysis and coordinate policymaking and implementation. The NSC is at the center of the interagency process, one through which relevant government agencies address foreign policy issues and help the president make and execute policy choices.

I. National Security Advisor

The national security advisor (formally assistant to the president for national security affairs), a senior advisor to the president, is at the heart of the NSC structure. Ideally, the national security advisor’s role is twofold: to offer advice to the president and to coordinate and manage policymaking. Because they have direct access to the president and do not represent a cabinet department such as the State Department or Defense Department, national security advisors are in a unique position to drive foreign policy decisions, manage the actors involved, and mitigate conflict throughout the decision-making process.

II. National Security Council Staff

The NSC staff consists of individuals from a collection of agencies that support the president, the vice president, and the administration. NSC staff members are generally organized into directorates that focus on regions or issues. The size and organization of the staff vary with each administration.

The NSC staff provides expertise for the variety of national security policy matters considered by the committees and the president. It manages numerous responsibilities, including preparing speeches, memos, and discussion papers and handling inquiries from Congress on foreign policy issues. Staff members analyze both immediate and long-term issues and help prioritize these issues on the interagency agenda.

III. Committee Structure

Committees are at the core of policy deliberation and policymaking in the NSC. They fall into four categories:

  • The highest-level is the National Security Council itself. Formal NSC meetings are chaired by the president and include individuals named by the National Security Act of 1947 as well as other senior aides the president invites.
  • The principals committee (PC) comprises cabinet-level officials who head major government departments concerned with national security, such as the secretaries of state and defense. The national security advisor traditionally chairs the principals committee.
  • The deputies committee (DC) includes the deputy leaders of the government departments represented on the principals committee and is chaired by the deputy national security advisor.
  • Policy coordination committees (PCCs) cover a range of regional areas and issues. Each committee includes officials who specialize in the relevant area or issue at one of the departments or agencies in the interagency system. PCCs are generally chaired by senior directors on the NSC staff. Much of the day-to-day work needed to formulate and implement foreign policy across the U.S. government happens at the PCC level.

This committee structure tackles both immediate crises such as an outbreak of conflict and enduring issues such as climate change. In the normal course of events, PCCs conduct analysis on an issue, gather views on it and its importance from various departments, formulate and evaluate policy options, and determine what resources and steps would be required to carry out those options. The deputies committee, meanwhile, manages the interagency process up and down. It decides what PCCs to establish and gives them specific assignments. It also considers information submitted by the PCCs, ensuring that it is relevant, complete, and clear, before relaying it to the principals committee or the full NSC.

The principals committee is the highest-level setting, aside from the NSC itself, for debating national security issues. It consists of the heads of the NSC’s component agencies—essentially all the members of the NSC except the president and vice president. Formal NSC meetings, which the president chairs, occur whenever the president sees fit. They consider issues that require the president’s personal attention and a direct presidential decision.

The goal of this committee structure is to foster consensus on policy options or highlight where and why consensus cannot be reached. If officials at one level agree on an issue, it may not need to go to senior officials for a decision. This practice reserves the president’s time, and that of the principals, for the most complicated and sensitive debates.

When a crisis erupts, however, issues may not follow the usual path up from the PCCs. In these cases, NSC staff members and officials in government departments and agencies generally draft papers drawing on their expertise, available intelligence, and any existing contingency plans. Policy options are then debated and decided at the appropriate level, depending on the nature and severity of the crisis. The policymaking process may also deviate from this model based on the preferences of each president.

For the purposes of Model Diplomacy’s NSC simulation, you will role-play the NSC meeting with the assumption that the committees described have already done their jobs and passed critical information to the highest-level decision-makers.

Presidential Decisions

When the president makes a policy decision, it may take the form of a verbal instruction recorded in a NSC staff document and shared with relevant departments and agencies. The president may also issue formal decisions in documents that lay out the administration’s policy and explain its rationale and goals. These documents have gone by different names under different presidents. President Donald J. Trump issues national security presidential memoranda, which replace the presidential policy directives and presidential study directives that President Barack Obama issued.

The president may also issue an executive order. In the past, presidents have issued executive orders for such purposes as facilitating sanctions against foreign individuals and establishing new offices in government departments to achieve foreign policy aims. For federal agencies, both national security directives and executive orders carry the full force and effect of law, though the president’s authority to issue these kinds of documents is sometimes questioned.

National Security Council meeting
President Bush leads a meeting of the National Security Council.

“These complex times have made clear the power and centrality of America’s indispensable leadership in the world.”

— Obama 2015 National Security Strategy

1.3 Departments and Agencies

Although many executive branch departments and agencies are involved in foreign policy and, depending on the issue, play a role in the NSC process, the Department of State, the Department of Defense, and the intelligence community form the core of the foreign policy bureaucracy. The Department of the Treasury, the Department of Homeland Security, and the Department of Justice often play crucial roles as well.

Department of State

The Department of State conducts the United States’ relations with other countries and international organizations. It maintains U.S. diplomatic presence abroad, issues visas for foreigners to enter the country, aids U.S. citizens overseas, and manages cultural exchanges and other programs to promote American interests. As head of the department, the secretary of state is the president’s principal foreign affairs advisor and has a keen understanding of the United States’ international relations, the relationships between foreign countries, and the behavior and interests of their governments.

Department of Defense

The Department of Defense carries out U.S. defense policy and maintains U.S. military forces. It includes the U.S. Army, Navy, Marine Corps, and Air Force, as well as an array of agencies with missions ranging from advanced technological research to defense cooperation with friendly countries. The department employs more than two million military and civilian personnel and operates military bases across the United States and abroad. The secretary of defense, the head of the department and the president’s principal defense policy advisor, stays up-to-date on the security situation in foreign countries and the possibilities and implications of U.S. military involvement. The chairman of the joint chiefs of staff is the highest-ranking member of the U.S. armed forces and the president’s top military advisor.

Intelligence Community

The U.S. intelligence community consists of seventeen agencies and organizations, including the Central Intelligence Agency (CIA), National Security Agency (NSA), and Federal Bureau of Investigation (FBI), which gather and analyze intelligence to help policymakers formulate and implement U.S. foreign policy. Each of these agencies has its own mission; for example, the NSA focuses on signals intelligence (information gathered from communications and other electronic signals) and the Defense Intelligence Agency on military information. The director of national intelligence, the president’s principal advisor on intelligence issues, oversees this network of agencies with the aim of ensuring that they work together and deliver the best possible information to U.S. policymakers.

Department of the Treasury

The Department of the Treasury carries out policy on issues related to the U.S. and global economies and financial systems. The secretary of the treasury, as head of this department, serves as one of the president’s chief economic advisors and is responsible for addressing a range of economic concerns, including growth, trade and investment, and the position of the U.S. dollar. The Treasury’s ten bureaus, which include the U.S. Mint and the Internal Revenue Service, do much of the department’s work, which ranges from collecting tax to printing currency and executing economic sanctions.

Department of Homeland Security

Created soon after the terrorist attacks of September 11, 2001, the Department of Homeland Security works to counter and respond to risks to American security. It focuses on issues such as terrorism prevention, border security and immigration, disaster response, and cybersecurity. Familiar agencies within the department include U.S. Customs and Border Protection, which checks travelers and goods coming into the United States; the U.S. Secret Service, which protects the president and investigates financial crimes; and the Transportation Security Administration, which ensures security at airports. The secretary of homeland security oversees the department and advises the president on relevant issues.

Department of Justice

The Department of Justice investigates and prosecutes possible violations of federal law, represents the U.S. government in legal matters, oversees federal prisons, and works more broadly to prevent and respond to crime. Agencies such as the FBI and the Drug Enforcement Administration are part of the department, as are divisions focusing on particular areas of law, such as national security and civil rights. Leading the department is the attorney general, who offers legal advice to the president and the heads of other departments, including on matters under discussion in the NSC.

Learn More
See More

Guide Glossary


alliance:an official partnership between two or more parties based on cooperation in pursuit of a common goal, generally involving security or defense.
attorney general:head of the Department of Justice and chief lawyer of the U.S. government. Among other duties, he or she offers advice on the legal aspects of proposed policies to the president and other department heads.


bilateral:undertaken between two entities, generally countries.
blockade:an act of war wherein a foreign military cuts off access to a specific location, usually a port, to impede deliveries of supplies. In 1962, President John F. Kennedy ordered a blockade of Cuba—calling it a “quarantine” to avoid the implication of declaring war—in response to Soviet missile activity on the island.


Cabinet:the group comprising the vice president of the United States and the heads of all fifteen federal executive departments, such as the secretaries of state, defense, commerce, labor, and education. Other officials may also have cabinet rank, depending on the administration.
Chairman of the Joint Chiefs of Staff (CJCS):the highest-ranking member of the U.S. armed forces. The CJCS does not exercise command authority over U.S. troops, but instead works with the leaders of the U.S. military services to fulfill his function as the top military advisor to the president and other senior officials.
chief of staff to the president:a close advisor to the president who is responsible for coordinating the implementation of presidential policy and managing the Executive Office of the President (EOP), which includes the national security staff among many other entities.
cyberwarfare:defensive and offensive actions taken by a government or nonstate actor in the realm of information network systems and digital infrastructure. Specific actions include planting computer viruses, mounting denial-of-service attacks to disrupt internet and network activity, and conducting electronic surveillance.


deputies committee (DC):the intermediate-level setting, below the principals committee, for debating issues in the National Security Council (NSC) system. Chaired by the deputy national security advisor, it comprises the second- and third-ranking leaders of the departments and agencies represented on the National Security Council. It manages the interagency process up and down, answering to the principals committee and assigning and reviewing the work of interagency policy committees.
director of national intelligence:the president’s principal advisor for intelligence-related matters and the head of the intelligence community, a network of seventeen agencies and organizations, such as the Central Intelligence Agency (CIA), Federal Bureau of Investigation (FBI), and Defense Intelligence Agency (DIA), that collect and analyze information to assist policymaking.


executive order (EO):a decision issued by the president that carries the full force and effect of law. An executive order usually instructs government departments and agencies to implement or modify particular policies or procedures.


foreign policy:a country’s attitudes and actions in the international arena. Foreign policy includes two principal elements: goals or interests as the country defines them, such as peace with one’s neighbors, and the means pursued to advance these interests, such as diplomatic negotiations, trade agreements, and military alliances. A country carries out its foreign policy through its dealings with other countries, international organizations such as the United Nations (UN), and nonstate actors such as corporations and advocacy groups.


interagency:involving two or more agencies. The National Security Council (NSC), for example, is an interagency forum, not a forum internal to any one agency.


multilateral:undertaken among three or more entities, usually countries. The term frequently describes organizations such as the United Nations (UN).


national security advisor (NSA):the so-called honest broker of the national security policy process and the president’s principal advisor on national security issues. The NSA manages the National Security Council (NSC) staff, chairs the principals committee, and coordinates and manages policymaking with the goal of ensuring effective policy development and implementation.
National Security Council (NSC):an interagency body that serves as the forum for the president to discuss and take action on the most critical national security issues facing the United States. Its membership has varied since its creation in 1947, and now includes the president, vice president, national security advisor, secretaries of state and defense, and a variety of other senior officials.
National Security Council (NSC) staff:the president’s national security and foreign policy personnel. The NSC staff receives direction from the president via the national security advisor, provides expertise on issues and regions, and collaborates frequently with employees from other government departments and agencies to carry out the interagency policymaking process.
national security presidential memorandum:a type of presidential directive, or official order from the president, on matters related to national security. Called different names by different administrations, these documents may initiate a review of current policy, reorganize the structure of the national security policy apparatus, or lay out new strategies.
nonstate actors:individuals or groups that do not belong to or act on behalf of a state. This may refer to nongovernmental organizations such as Amnesty International, media outlets such as the New York Times, or terrorist groups such as al-Qaeda.


policy coordination committees (PCCs):the lowest-level setting for debating issues in the National Security Council (NSC) system and the home of much of the day-to-day work needed to formulate and implement U.S. foreign policy. Often chaired by a senior director on the NSC staff, PCCs develop, coordinate, and carry out policy options in distinct regional and functional areas.
principals committee (PC):the highest-level setting, aside from the National Security Council (NSC) itself, for debating issues in the NSC system. Generally chaired by the national security advisor, it comprises cabinet-level officials who head major government departments concerned with national security, such as the secretaries of state, defense, and homeland security, and other senior officials.


sanction:a tool of statecraft, frequently involving economic measures such as asset freezes and trade restrictions, used to exact a certain behavior or outcome from another party. The U.S. and EU sanctions against Russian companies and individuals that aim to encourage Russia to end its interference in Ukraine are an example.
secretary of defense:the principal defense policy advisor to the president and head of the Department of Defense, which oversees the formulation and execution of defense policy and manages U.S. military forces.
secretary of energy:the head of the Department of Energy, which executes U.S. policy on energy, environmental, and nuclear issues and oversees seventeen national scientific research laboratories.
secretary of homeland security:the head of the Department of Homeland Security since its creation after the attacks of September 11, 2001. This department works to protect U.S. security by implementing federal policy concerning terrorism prevention, border security, immigration, disaster response, and cybersecurity.
secretary of state:the president’s chief foreign affairs advisor, the country’s chief diplomat, and the head of the Department of State, which conducts the United States’ relationships with foreign countries and international organizations.
secretary of the treasury:one of the president’s chief economic advisors and head of the department of the treasury, which carries out policy on issues related to the U.S. and global economies and financial systems. The department is home to the U.S. Mint and Internal Revenue Service, among other agencies.
special operations forces:elite U.S. military units, such as Navy Sea, Air, and Land (SEAL) teams and Army Special Forces, grouped under U.S. Special Operations Command (SOCOM). They conduct specialized and often sensitive missions that include guerrilla warfare, counterterrorism raids, counterproliferation, and advanced reconnaissance.


tariff:a tax on goods arriving from a foreign country, generally used as a tool of trade and foreign policy to penalize adversaries or favor allies or domestic producers.


U.S. permanent representative to the United Nations (UN):the ambassador-level official who advances U.S. foreign policy interests in the bodies and forums of the UN system.
unilateral:undertaken by only one entity, generally a country.


vice president:the second-highest-ranking official of the U.S. government and first in line to assume the presidency if the president dies, resigns, or becomes unable to serve. Though given only one responsibility in the Constitution—to serve as president of the U.S. Senate, with the power to break ties—the vice presidency has become a visible part of the modern White House. Today’s vice presidents undertake a variety of functions, from serving as an all-purpose presidential advisor to carrying out diplomatic trips abroad. The personality of the individual who occupies this post and his or her relationship with the president define the scope of the role.
Case Notes Sections
Korean War cover image
Soldiers in Korean War.

“If we let Korea down, the Soviet[s] will keep right on going and swallow up one piece of Asia after another.” 

— Harry Truman, president of the United States, September 25, 1950

2.1 Introduction

On June 25, 1950, Soviet-backed North Korea invaded U.S.-backed South Korea, sending its forces across the agreed boundary at the thirty-eighth parallel in an attempt to bring the entire peninsula under its control. In response, President Harry S. Truman approved U.S. military action to help South Korea. Truman and others believed what was at stake was not simply U.S. interests in Asia but also the confidence of U.S. allies everywhere in U.S. willingness to stand up to communist aggression. The military action was in accordance with UN Security Council Resolution 83—advanced by the United States—which authorized the use of force to “repel the armed attack.”

After several weeks of fighting, U.S. and South Korean forces were defending an area called the Pusan perimeter, a zone of southeastern South Korea around the port of Pusan, against North Korea’s southward advance. General Douglas MacArthur, who was commanding U.S. and allied forces as part of the UN mission, was also making plans for a landing at Inchon, near the South Korean capital Seoul.

A successful Inchon landing would mean the prospect of swiftly liberating South Korea. Truman faced a weighty decision. Should the United States simply restore the status quo ante bellum, pushing North Korea’s military back to the thirty-eighth parallel? Or should U.S. forces, leading UN forces in what Truman called a “police action,” advance into North Korea and try to unify the peninsula? On September 1, 1950, Truman pledged U.S. help for the Koreans “to be free, independent, and united.” But there was no consensus among administration officials, members of Congress, and other leaders on how far U.S. involvement should extend.

A U.S. move into North Korea would therefore bring the risk of war with the Soviet Union, China, or both. However, it would also carry the possibility of a unified peninsula, at peace, under leadership friendly to the United States. Merely restoring the status quo would reduce the risk of war with the communist powers. It would also, however, preserve a hostile North Korean leadership and leave the divided peninsula as an open wound, and potential battleground, in the intensifying Cold War.

Learn More
See More
Soldiers in Korean War.
Soldiers in Korean War.

“The forces shaping Korea into a nation arose from its unfortunate proximity to three powers, China, Japan, and Russia. The periodic surges of ambition in each of these neighbors turned Korea into a battleground and a spoil.”

— James F. Schnabel, historian with the Office of the Joint Chiefs of Staff, 1972

2.2 Background

Slightly smaller than the United Kingdom, the Korean Peninsula juts southward from China between the Yellow Sea and the Sea of Japan. The peninsula’s northern edge shares a long border with China and a short one with Russia; to the east, it shares a maritime boundary with Japan.

For much of the early twentieth century, Korea was a protectorate of Japan. Japan seized control of the peninsula—which had been ruled for centuries by the Choson dynasty—in the First Sino-Japanese War (1894–95) and maintained its control despite challenges from Russia and frequent domestic uprisings. Japan’s grip on the peninsula was tight politically, economically, and culturally. Japanese authorities outlawed social and political organizations, banned the teaching of the Korean language, and forced the population to speak Japanese and adopt Japanese names. Japan did industrialize the peninsula, building highways, railroads, and factories, but much of this effort was gradually directed toward military use by an increasingly aggressive imperial Japan.

By the late 1930s, Japan was well into its campaign of conquest throughout East Asia. In 1931, it had invaded and seized Manchuria, a resource-rich region in northeast China, and renamed it Manchukuo. It followed up in 1937 with a full-scale invasion of China, starting the Second Sino-Japanese War. In 1936 and 1937, Japan formalized its friendship with Nazi Germany and Fascist Italy by signing the Anti-Comintern Pact, forming the alliance that would come to be known as the Axis powers.

When war broke out in Europe in 1939, Japan saw an opportunity to seize European colonies and grow its empire. However, it faced growing economic sanctions from the United States and its Western allies, who were worried about Japan’s imperial expansion. On December 7, 1941, the Japanese carried out a surprise military strike on the U.S. naval base at Pearl Harbor in Hawaii. The attack, intended to avoid an extended conflict by debilitating the U.S. fleet, instead brought the United States into World War II.

During the war, Japan brutally exploited Korea’s people. It drafted more than 240,000 men into the military, as soldiers and civilian employees. More than five million men and women were conscripted to work in war-related industries under dangerous conditions, and some 670,000 were forcibly brought to Japan. Hundreds of thousands died. But the most notorious abuse involved the so-called comfort women. Up to two hundred thousand Korean women were kidnapped to serve as sex slaves in military brothels, or comfort stations, for Japanese soldiers. Japan contests its responsibility for the treatment of these women to this day.

By early 1945, the war in the Pacific was entering its final phase. U.S. leaders started to think about how to handle the territories Japan had acquired since beginning its expansionist campaign in the late nineteenth century. At the Yalta conference in Crimea in February, U.S. President Franklin D. Roosevelt and Soviet leader Joseph Stalin, who were allies against Nazi Germany in the war in Europe, agreed to establish an international trusteeship for Korea following Japanese surrender. This agreement, though, was only a general framework. The precise arrangements for governing a postwar Korea were not finalized.

The Soviet Union declared war on Japan on August 8, 1945; shortly thereafter, Soviet forces invaded Korea and Manchuria. U.S. military leaders feared that, if the Soviet Union ended up occupying Korea in the course of the conflict, it would never cede control. This concern spurred the U.S. government to finalize a formula for administering the peninsula. U.S. officials hurriedly proposed the thirty-eighth parallel north as a demarcation line between U.S. and Soviet forces, cutting the peninsula almost in half. This line was intended as a temporary operational boundary that would hinder Soviet ambitions and prevent confusion among military forces operating in Korea.

The order came down on August 17, 1945, two days after Japan’s surrender ended World War II. (Japan had surrendered days after the United States dropped atomic bombs—the only two ever used in combat—on Hiroshima and Nagasaki, devastating the two cities and killing some 170,000 people.) The Soviet Union would accept the Japanese surrender of weapons and troops and take control of the territory north of the thirty-eighth parallel. South of the parallel, these tasks would fall to the United States.

Temporary peace was thus brought to the Korean Peninsula after the end of the war. The political and economic situation, though, remained complex and unstable. U.S. troops landed in Korea on September 8, 1945, following the Soviet troops, who had arrived the previous month. Because Korea had been a Japanese colony since 1910, no Korean government was in place ready to reclaim authority. The political scene was fragmented as various leaders jostled for power. One of these was Kim Il-sung, a military leader with close connections to the Soviet Union who would become the first leader of North Korea. Other contenders were ultranationalists oriented more toward the West. This camp included Syngman Rhee, who had earned a doctorate at Princeton University and, with U.S. backing, would become the first leader of South Korea.

Korea’s economy, meanwhile, was suffering. When the Japanese departed after World War II, many companies were left without managers, capital, and other resources, leading to unemployment and shortages of vital goods. The peninsula’s division at the thirty-eighth parallel did not help. Korea’s heavy industry and energy production were concentrated in the north, leaving the south’s primarily agrarian economy dependent on electricity transmission and transport of other essentials. This, along with the return of millions of Koreans from elsewhere in the region, caused significant social unrest and protests against the U.S. military government in the south.

At first, the United States and the Soviet Union shared a vision for a united, independent Korea. The foreign ministers of the World War II allies, meeting in December 1945 in Moscow and building on the plan devised at the Yalta conference in February, agreed that Korea would have a five-year trusteeship. Attempts to fulfill this vision stumbled, however. A joint U.S.-Soviet commission met occasionally in 1946 and 1947 but was unable to establish a Korean government because the United States and Soviet Union disagreed on who should participate.

Meanwhile, the division on the peninsula remained stark. The south was disorganized, afflicted by economic instability, political differences among Koreans, and uncertain U.S. policy. In the north, by contrast, the Soviet Union smartly consolidated control. It created administrative bodies and a North Korean Workers’ Party that united various left-wing groups. At the same time, Soviet-encouraged land reform, which redistributed land from Japanese and Korean landowners to poor farmers, drove thousands of former landowners and Japanese collaborators into the southern part of the peninsula.

Failing to make progress with Moscow on an acceptable path for Korean independence, the Truman administration took the issue to the UN General Assembly in September 1947. World leaders had established the United Nations just two years earlier, vesting in it their collective hopes of preventing a third world war. In the General Assembly, the main UN deliberative body, the United States continued to advance the vision of a united, independent peninsula. In November 1947, the General Assembly adopted UN Security Council Resolution 112, which asserted “that the national independence of Korea should be re-established and all occupying forces then withdrawn at the earliest possible date.” To facilitate this plan, the resolution established the UN Temporary Commission on Korea, which would pave the way for elections for a national assembly. This assembly was to set up a government that would assume full administrative responsibilities and work with the United States and Soviet Union to clear Korea of occupying troops.

Despite the commission, the Korean Peninsula moved no closer to unified governance. Instead, politics continued to evolve separately on either side of the thirty-eighth parallel. Rhee, by now an influential, U.S.-backed nationalist leader, favored independence as soon as possible—even though a declaration of independence would have effect only in the south as long as the United States and the Soviet Union remained at loggerheads. In a UN-supervised election in May 1948 for a constitutional assembly in the south, Rhee came out in front. Under his leadership, the assembly adopted a constitution outlining a presidential system of government. The Republic of Korea, which remains the official name of South Korea, was proclaimed on August 15, 1948. Rhee took office in Seoul as its first president.

North of the thirty-eighth parallel, the Soviet Union refused to admit the Temporary Commission. Four days after the proclamation of the Republic of Korea, authorities in the north cut power transmission to the south, further reinforcing the peninsula’s division. Less than a month later, the Democratic People’s Republic of Korea, the official name of North Korea, was born, its capital in Pyongyang. Its first leader, Kim Il-sung, claimed jurisdiction over the entire peninsula. By the end of 1948, he had solidified control over the north’s administrative structures, military forces, and Communist Party.

The United States kept military forces in South Korea until 1949, but its support for Rhee’s government was half-hearted. U.S. officials were unsure of Seoul’s political future and doubted its strategic value. The United States declined to commit to defending South Korea even though it had made such commitments to Japan and the members of the new North Atlantic Treaty Organization (NATO) in the immediate post–World War II years. (In a speech on January 12, 1950, Secretary of State Dean Acheson did not include Korea in what he described as a U.S. defensive perimeter.) The South Korean government established its own army in September 1948. However, a rebellion by some army units the following month, and a purge thereafter, left the force weak. By 1950, it had fewer than one hundred thousand soldiers and lacked advanced equipment such as tanks, heavy weapons, and combat aircraft.

The contrast with North Korea was stark. Although the Soviet Union had withdrawn its forces in late 1948, focusing instead on increasing its control in Eastern Europe, it continued to provide training and arms to North Korean forces. With this assistance, by mid-1950 Pyongyang had built up a force of 150,000 to 200,000 troops. The North Korean People’s Army had fearsome Soviet weapons, including tanks and fighter planes, at its disposal.

Fueled by his military might and ambitions to control the entire peninsula, Kim Il-sung sought Stalin’s support for an invasion of the south. At first, Stalin resisted. In spring 1950, however, he relented and approved Kim’s plan. Kim also sought support—at Stalin’s encouragement—from the Chinese leader Mao Zedong, who had recently emerged victorious in the Chinese civil war and successfully pushed nationalist forces offshore to Taiwan. Early on the morning of June 25, 1950, North Korean soldiers crossed the thirty-eighth parallel. The Korean War began. The main offensive was aimed at the South Korean capital, Seoul, which fell in only three days.

The United States, under Truman, responded both diplomatically and militarily. On the diplomatic front, it immediately secured UN Security Council Resolution 82, calling for the invasion to halt. Resolution 83, passed two days later, on June 27, called on UN member states to provide “such assistance to the Republic of Korea as may be necessary.” The Soviet Union, as a permanent member of the Security Council, could have vetoed these resolutions. However, the Soviet Union had been boycotting Security Council meetings after the defeat of its proposal to replace the nationalist Chinese delegation holding the council’s permanent seat with delegation from Mao’s communist China.

Truman initially gave military equipment to the South Korean army and deployed U.S. aircraft and ships. As South Korea’s military faltered, he allowed limited U.S. ground troops to enter the fight in early July. On July 7, UN Security Council Resolution 84 put the United States in command of all military operations to assist the South Koreans. Under MacArthur’s command, the UN mission initially struggled. The disorganized, ill-equipped South Korean army was no match for the invading North Koreans. U.S. personnel, still recovering from World War II, had to contend with equipment shortages, refugees fleeing the fighting, and even a lack of water.

By the end of the summer, about two months after the war began, more than eighty thousand U.S. troops were in Korea. They were fighting alongside some ninety thousand South Korean troops and a 1,600-man British contingent. These allied forces held only the Pusan perimeter in southeastern South Korea—North Korean soldiers had overrun the rest of the peninsula. Communist control, which the United States had sought to limit since the closing months of World War II, now threatened all of Korea.

To reverse the turn of events, MacArthur was planning a risky landing of forces at Inchon, an area on the west coast of South Korea near Seoul. He aimed to cut off enemy supply lines behind the North Korean troops, which had advanced farther south. The aim was to divide the enemy forces and break their hold on Seoul, enabling South Korea’s government to eventually regain control. The Inchon landing would be an amphibious assault: troops would arrive by sea and proceed on to land. This plan echoed the D-Day landings on the beaches of Normandy, in France, on June 6, 1944. Those assaults were costly but spectacularly successful and turned the tide against Nazi Germany in the European theater of World War II.

Should the Inchon landing succeed, the liberation of South Korea would be at hand. With that could come an opportunity to unify the peninsula, as U.S. leaders had envisioned since the surrender of Japan. But realizing this opportunity would require invading North Korea, which could bring the United States into conflict with the Soviet Union, China, or both.

Soldiers in Korean War.
Truman with advisers.

I am convinced that there will be no permanent peace and stability in Korea as long as the artificial division at the 38th parallel continues.”

— John Allison, director of the Office of Northeast Asian Affairs at the Department of State, July 1950

2.3 U.S. Policy Debate

Inside the Truman administration, arguments over what the United States should aim to do in Korea began almost as soon as the North Koreans invaded the south. Perhaps the most critical question was whether and how China or the Soviet Union would intervene if the United States tried to reunify the Korean Peninsula.

On the one hand, Truman was cautious. He sought to ensure that the United States would not overcommit to Korea or slip into conflict with Moscow. As he wrote in his memoir Year of Decisions, “Every decision I made in connection with the Korean conflict had this one aim in mind: to prevent a third world war and the terrible destruction it would bring to the civilized world. This meant that we should not do anything that would provide the excuse to the Soviets and plunge the free nations into full-scale all-out war.” On the other hand, administration officials recognized a potential opportunity to deal a devastating blow to global communism and reunify Korea under a democratic, U.S.-backed government.

The initial U.S. goal, in the opening weeks of the conflict, was simply to drive the North Koreans back to their own territory. Truman agreed with an early suggestion by Secretary of the Army Frank Pace that U.S. military operations north of the thirty-eighth parallel should be strictly limited. He authorized military operations with the specific goal of restoring that parallel as the border.

Many administration officials, though, advanced the view that U.S. aims should go further. John Allison, director of the State Department’s Office of Northeast Asian Affairs, was among them. In a July 1, 1950, memo to Assistant Secretary of State for Far Eastern Affairs Dean Rusk, Allison wrote, “I am convinced that there will be no permanent peace and stability in Korea as long as the artificial division at the 38th parallel continues.” Other major State Department figures, including advisor John Foster Dulles, generally shared a desire to pursue full unification of the peninsula. They were more cautious than Allison, however, and feared war with the Soviet Union or China.

Military leaders, for their part, were eager to proceed north of the thirty-eighth parallel, though their foremost goal was not necessarily to reunify the peninsula. Instead, it was to devastate the North Korean military so that it could not invade South Korea again. Chairman of the Joint Chiefs of Staff Omar Bradley wrote in his autobiography A General’s Life that this was the military’s “unanimous” position: “We believed that MacArthur should not be restrained at the 38th parallel.”

This view certainly pleased MacArthur, who had ambitions of occupying and reunifying the entire peninsula. In mid-July, just weeks after the war began, MacArthur told other military leaders, “I intend to destroy and not to drive back the North Korean forces. I may need to occupy all of North Korea.” On August 8, W. Averell Harriman, special assistant to the president, met MacArthur in Tokyo. MacArthur, in Harriman’s telling, was confident that elections could he held in both North and South Korea following a military victory—and that MacArthur had “no doubt of an overwhelming victory for the non-Communist parties” in both the South and the North.

The opposite view—that the United States should limit itself to pushing the North Koreans back—was less widespread during the summer of 1950. Some officials, though, did counsel restraint. This perspective came most notably from the State Department’s policy planning staff, a unit intended to provide analysis that goes beyond day-to-day issues. George Kennan, who had established the staff and served as its first director, was one of the loudest voices warning of the potential risks of intervention north of the thirty-eighth parallel. Kennan’s successor as director of the policy planning staff, Paul Nitze, and other members of the unit shared Kennan’s skeptical view. A July 22 draft memo prepared by the one staff argued: “The disadvantages of a failure to attain the complete independence and unity of Korea after the North Korean forces have been driven back to the 38th parallel must be weighed against the risk of a major conflict with the USSR or Communist China that such a settlement might well involve.” In other words, stopping U.S. action at the thirty-eighth parallel would be bad, but war with the Soviets or Chinese could be worse.

Case Notes Glossary


38th parallel:a line of latitude established as the boundary between the northern and southern parts of Korea after World War II. Following the defeat of Japan, which had occupied Korea, territories north of the line were to be administered temporarily by the Soviet Union while southern territories were to be administered temporarily by the United States.


aggression:hostile action by one country or party toward another, typically involving the use of military force. An unprovoked attack by one country on another would generally be considered aggression, while the use of force in self-defense would not. The UN Charter gives the Security Council the authority to “determine the existence of any . . . act of aggression.”
annexation:the addition of territory to another, existing state, often without the consent of the annexed party. In 2014, Russia annexed the peninsula of Crimea—which then belonged to the separate country of Ukraine—and now considers it part of Russia. A referendum occurred prior to annexation in which Crimeans voted to join Russia, but the United States and other governments question the legitimacy of both the referendum and the annexation.


client state:a country that is dependent on another, more powerful one. The patron typically uses economic aid, military power, and other tools to maintain the client’s loyalty. Client states are often ideologically aligned with their patrons and intended to extend the patron’s influence. Although they are notionally sovereign, client states’ dependence on larger powers often limits their autonomy to pursue their own policy choices. However, clients can gain military and economic aid in exchange for their support.
Cold War:the contest between the United States and the Soviet Union—and, by extension, capitalist democracy and communist dictatorship—that characterized international politics between the post–World War II years and the early 1990s. Deemed a “cold” war because the rivalry never resulted in direct warfare between the two, the contest nevertheless sparked proxy wars in other countries and many close calls, such as the Cuban Missile Crisis in 1962.
communism:a political ideology that advocates for public ownership of essential resources such as factories, farms, and mines in a society where wealth is divided equally among citizens. Envisioned by German philosopher Karl Marx in the nineteenth century, communism is seen as an ideological rival to Western capitalism; the contest between these ideologies was a central dynamic of the Cold War and the Korean War. The political ideology also contributed to the division of the Korean peninsula, with the Democratic People’s Republic of Korea (DPRK) established in the North with the Soviet Union’s support and the U.S.-backed Republic of Korea (ROK) in the South.


expansionism:a policy approach in which states seek to expand their territories and broaden their influence. The term refers in particular to efforts to physically expand a country by acquiring additional territory, generally through military conquest.


Korean Empire:a political entity in place from 1897 to 1910 that encompassed the Korean Peninsula and replaced the Choson dynasty, which had ruled the peninsula for five hundred years. Proclaimed by Gojong, the empire was intended to be the start of a sovereign and independent Korea, free of influence from powerful states such as China, Japan, and Russia. Its brief tenure ended with Japan’s annexation of Korea in 1910.


Marxism:a broad ideology stemming from the teachings of nineteenth century scholars Karl Marx and Friedrich Engels. Although their work has influenced the development of a wide range of theories, the centerpiece is the view that social change must occur through a violent revolution of working class individuals against the wealthy elite. Marxist interpretations of class relations are a core feature of communism, which fueled the political thinking of several famed leaders throughout the twentieth century. These include the Soviet leader Joseph Stalin and the Chinese leader Mao Zedong.
modernization:the transition of a state toward a modern, industrialized economy. This includes adopting new technologies, shifting large parts of the workforce from agriculture to industry, and effecting other transformations. Modernization generally brings higher living standards and new opportunities, at least for some, as well as social disruptions.


nationalism:a sense of pride in and loyalty to a national identity, which may or may not correspond to a sovereign state. This identity is often based on common traits such as ethnicity or language.


partition:to divide or break apart, often used in reference to territory.
peninsula:a piece of land surrounded by water on three sides. The word comes from the Latin words for “almost” and “island.”
protectorate:a locally autonomous territory that is dependent upon and controlled by a more powerful sovereign state. A protectorate often receives aid, military protection, and preferential trade treatment from the powerful state.


Russo-Japanese War:a conflict between Russia and Japan between February 1904 and September 1905. The war, sparked by frictions over territorial expansion in Manchuria and Korea, resulted in a decisive victory for Japan. It was concluded by the Treaty of Portsmouth, mediated in part by U.S. President Theodore Roosevelt, in which Russia recognized Japan’s claim over Korea. Japan’s victory emboldened it to pursue an expansionist policy in the next several decades.


Sino-Japanese War:a conflict in 1894 and 1895 between Japan and China. Japan’s victory and subsequent occupation of Korea, Taiwan, and other territories marked the beginning of Japan’s Imperial expansion. This expansion, including Japan’s invasion and annexation of Manchuria in 1931, led in turn to the outbreak of the Second Sino-Japanese War in 1937. Japan’s aggression throughout the Pacific also led to World War II in that region.
sovereignty:supreme or absolute authority over a territory.
Soviet Union:officially the Union of Soviet Socialist Republics (USSR), the political entity in existence from the 1917 Bolshevik Revolution to the early 1990s that encompassed modern-day Russia and fifteen neighboring countries. With a communist economy and totalitarian system of government, the Soviet Union grew to be the other major superpower in the post–World War II era. As such, it was the principal antagonist of the United States during the Cold War.


trusteeship:the supervisory administration of a territory by another country. The intention is generally to help the territory prepare for independence. One of the core functions of the United Nations, upon its founding in 1945, was to supervise various territories governed under trusteeship. Over time, all became autonomous or independent.


UN General Assembly:the main deliberative body of the United Nations. Of the six core parts of the organization, it is the only one that includes all 193 member states. Each country, large or small, has one vote. In addition to adopting nonbinding resolutions on a variety of topics, the General Assembly performs functions such as admitting new members to the United Nations and creating the UN’s budget. The General Assembly adopted many resolutions during the lead-up to the Korean War, including Resolution 195 which recognized the Republic of Korea under Syngman Rhee as Korea’s legitimate government.
United Nations:an international organization composed of 193 independent member states that aims to promote international peace and stability, human rights, and economic development. The United Nations was established in 1945 and remains the only organization with practically universal membership among the world’s countries. It includes the Security Council, General Assembly, and a range of other bodies; a secretary-general, currently Ban Ki-moon, serves as its leader. The United Nations also has an array of affiliated programs and agencies, such as the United Nations Children’s Fund (UNICEF), the United Nations Development Program (UNDP), and the United Nations Educational, Scientific, and Cultural Organization (UNESCO).
United Nations Security Council:the principal UN body charged with maintaining international peace and security. The UN Security Council is the only UN body with the authority to pass resolutions that are binding on the 193 UN member states. It includes five permanent member states (China, France, Russia, the United Kingdom, and the United States) and ten rotating members elected to two-year terms. The five permanent members have veto power over resolutions, making their agreement necessary for a resolution’s approval. This structure provides strong international legitimacy to Security Council resolutions but also stymies action when the major powers disagree.
Role Play Sections
Students at a Model Diplomacy simulation.
Students at a Model Diplomacy simulation.
Students at a Model Diplomacy simulation.

3.1 Role

Welcome to your role as a participant in the National Security Council (NSC)! You should have received an email with your role assignment, but if you did not, you can view your assignment by clicking on the “My Simulations” tab on your account page. At this point, you should have reviewed essential background information about the NSC, read the case, watched the accompanying videos, and perused some of the additional reading. Whether you have been assigned a specific role as an individual or part of a group, or as a general advisor to the president, we suggest you read the case once again to identify material that is particularly relevant to your role or that requires further investigation. After that, you will conduct independent research as you write your position memo and prepare for the role-play.

There are four subsections that follow. Research and Preparation (3.2) will aid your research for the position memo and provide additional reading to guide your research; the Guide to the Memoranda (3.3) provides information about position memos and an example; and the Guide to the Role-Play (3.4) provides more information on the in-class role-play.

You can learn about your role by reading the information provided on your role sheet, which can be found in the Guide to the Role-Play section (3.4).  Review this information thoroughly and often, as your objectives and strategy in the position memo and role-play will be shaped by the institutional perspective of the role you have been assigned (unless you are playing a general advisor). After you finish the role-play and subsequent debrief, you will have an opportunity to share your personal thoughts and recommendations on this case in a policy review memo (Section Four, Wrap-up).

Students at a Model Diplomacy simulation.
Students at a Model Diplomacy simulation.
Students at a Model Diplomacy simulation.

3.2 Research and Preparation

Your role sheet contains three parts: a description of your role, issues for consideration, and research leads. The role description details the position you will portray in the role-play. The issues for consideration will guide your thinking and assist you in approaching the case from the perspective of your assigned role. Most relevant, however, are the research leads. Going beyond the reports and articles linked to throughout the case and in the reading list, these research leads provide suggested materials and topics for further research specifically relevant to your assigned role. Below are some tips to review as you prepare for the role-play exercise.

Research and Preparation

  • Draw on the case notes, additional case materials, and your own research to familiarize yourself with

    • the goals of the NSC in general and of this NSC meeting in particular;
    • the U.S. interests at stake in the case and their importance to national security;
    • your role and your department or agency, including its purpose and objectives in the government and on the NSC;
    • the aspects of the case most relevant to your role;
    • the elements that a comprehensive policy proposal on the case should contain; and
    • the major debates or conflicts likely to occur during the role-play. You need not resolve these yourself, of course, but you will want to anticipate them in order to articulate and defend your position in the NSC deliberation.
  • Set goals for your research. Know which questions you seek to answer and refer back to the case notes, additional readings, and research leads as needed.
  • Make a list of questions that you feel are not fully answered by the given materials. What do you need to research in greater depth? Can your classmates help you understand these subjects?
  • Using the case materials, additional readings, and discussions with your classmates, weigh the relative importance of the U.S. interests at stake in the case. Determine where trade-offs might be required and think through the potential consequences of several different policy options.
  • Conduct your research from the perspective of your assigned role, but be sure to consider the full range of U.S. interests at stake in the case, whether diplomatic, military, economic, environmental, moral, or otherwise. This will help you strengthen your policy position and anticipate and prepare for debates in the role-play.
  • Consider what questions or challenges the president or other NSC members might raise regarding the options you propose and have responses ready.



  • Consult a wide range of sources to gain a full perspective on the issues raised in the case and on policy options. Seek out sources that you may not normally use, such as publications from the region(s) under discussion, unclassified and declassified government documents, and specialized policy reports and journals.
  • Remember: Wikipedia is not a reliable source, but it can be a reasonable starting point. The citations at the bottom of each entry often contain useful resources. 
  • Just as policymakers tackle issues that are controversial and subject to multiple interpretations, so will you in your preparation for the writing assignments and role-play. For this reason, evaluate your sources carefully. Always ask yourself:
    • When was the information produced? Is it still relevant and accurate?
    • Who is writing or speaking and why? Does the author or speaker have a particular motivation or affiliation that you should take into account?
    • Where is the information published? Determine the political leanings of journals, magazines, and newspapers by reading several articles published by each one.
    • Who is the intended audience?
    • Does the author provide sufficient evidence for his or her analysis or opinion? Does the author cite reliable and impartial sources?
    • Does the information appear one-sided? Does it consider multiple points of view?
    • Is the language measured or inflammatory? Do any of the points appear exaggerated?
  • Take note of and cite your sources correctly. This is important not just for reasons of academic integrity, but so that you can revisit them as needed.
  • Ask your teacher which style he or she prefers you use when citing sources, such as Modern Language Association (MLA), Chicago Manual of Style, or Associated Press (AP).

Reading List 


2.1 The Issue

“The United Nations at War,” New York Times, July 10, 1950, http://nytimes.com/1950/07/10/archives/the-united-nations-at-war.html.

United Nations Security Council, Resolution 82, Resolution of 25 June, 1950,  http://www.un.org/en/ga/search/view_doc.asp?symbol=S/RES/82(1950).

J. R. Wiggins, “Should We Cross the 38th Parallel?,” Washington Post, August 13, 1950, http://search.proquest.com/docview/152282728?pq-origsite=summon.


2.2 Background

Radio and Television Address to the American People on the Situation in Korea, July 19, 1950, in Public Papers, Harry S. Truman 1945-1953, https://trumanlibrary.org/publicpapers/index.php?pid=823&st=&st1=.

Intelligence Estimate Prepared by the Estimates Group, Office of Intelligence Research, Department of State, June 25, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 148–154, http://history.state.gov/historicaldocuments/frus1950v07/pg_148.

“Crisis in Korea,” Sydney Morning Herald, April 18, 1947, http://news.google.com/newspapers?nid=1301&dat=19470418&id=BooQAAAAIBAJ&sjid=FJMDAAAAIBAJ&pg=1634,2219250.


2.3 U.S. Policy Debate

The President of the Republic of Korea (Rhee) to President Truman, July 19, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 428–430, http://history.state.gov/historicaldocuments/frus1950v07/pg_428.

Draft Memorandum Prepared by the Policy Planning Staff, July 22, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 449–454, http://history.state.gov/historicaldocuments/frus1950v07/pg_449.

Memorandum by the Director of the Office of Northeast Asian Affairs (Allison) to the Director of the Policy Planning Staff (Nitze), July 24, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 458–461, http://history.state.gov/historicaldocuments/frus1950v07/pg_458.




The Secretary of State to the Acting Political Adviser in Japan (Sebald), July 1, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 278–279, http://history.state.gov/historicaldocuments/frus1950v07/pg_278.

Dean Acheson to Paul Nitze, July 12, 1950, in Acheson Papers, Secretary of State Files, http://trumanlibrary.org/whistlestop/study_collections/koreanwar/documents/index.php?documentid=ki-13-4&pagenumber=1.

Memorandum by the Director of the Office of Northeast Asian Affairs (Allison) to the Assistant Secretary of State for Far Eastern Affairs (Rusk), July 1, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 272, http://history.state.gov/historicaldocuments/frus1950v07/pg_272.

The British Prime Minister (Attlee) to President Truman, July 6, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 314–315, http://history.state.gov/historicaldocuments/frus1950v07/pg_314.

The United States Representative at the United Nations (Austin) to the Secretary of State, June 26, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 171–172, http://history.state.gov/historicaldocuments/frus1950v07/pg_171.

Erwin D. Canham, “Power for Peace,” New York Times, July 30, 1950, http://timesmachine.nytimes.com/timesmachine/1950/07/30/113395701.pdf.

Draft Memorandum Prepared in the Department of State for National Security Council Staff Consideration Only, August 23, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 635–639, http://history.state.gov/historicaldocuments/frus1950v07/pg_635.

“Final Assault on Seoul: U.S. Forces Meeting  Stiffer Resistance,” Glasgow Herald, September 22, 1950, http://news.google.com/newspapers?nid=2507&dat=19500922&id=cptAAAAAIBAJ&sjid=XJUMAAAAIBAJ&pg=5412,1572950

Intelligence Estimate Prepared by the Estimates Group, Office of Intelligence Research, Department of State, June 25, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 148–154, http://history.state.gov/historicaldocuments/frus1950v07/pg_148.

“Invasion of South Korea Won’t Start New World War, Confused Washington Predicts,” Wall Street Journal, June 27, 1950, http://search.proquest.com/docview/131815190?pq-origsite=summon.

The Joint Chiefs of Staff to the Commander in Chief, Far East (MacArthur), July 1, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 271, http://history.state.gov/historicaldocuments/frus1950v07/pg_271.

Richard J.H. Johnston, “South Koreans Ask All-Country Rule: Regime Wants UN Force to Go Beyond 38th Parallel and Set Up Unified Control,” New York Times, September 2, 1950, http://timesmachine.nytimes.com/timesmachine/1950/09/02/94272142.pdf.

The Ambassador in the Soviet Union (Kirk) to the Secretary of State, July 1, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 277–278, http://history.state.gov/historicaldocuments/frus1950v07/pg_278.

The Ambassador in the Soviet Union (Kirk) to the Secretary of State, August 11, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 557–559, http://history.state.gov/historicaldocuments/frus1950v07/pg_557.

“Korea: A Chronology of Principal Events, 1945–50,” The World Today 6, no. 8 (1950): 319–330. http://jstor.org/stable/pdf/40392341.pdf?refreqid=excelsior:1473debd4053c1910c367040c455425f.

“Korea Reports: Reds Sweep Southward and Advance in Yongdong Sector,” New York Times, July 25, 1950, http://timesmachine.nytimes.com/timesmachine/1950/07/25/113392236.pdf.

Henry R. Lieberman, “Mao’s Ties With Stalin Seen as Much Stronger: All Peiping Policies Are Shaped to Fit Pattern f the Communist World,” New York Times, August 27, 1950, http://timesmachine.nytimes.com/timesmachine/1950/08/27/121632239.pdf.

Life, July 31, 1950, 20–26, http://books.google.com/books?id=7EoEAAAAMBAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false.

“Moscow, China, and Korea,” New York Times, July 21, 1950, http://nytimes.com/1950/07/21/archives/moscow-china-and-korea.html.

Memorandum of Conversations, by Mr. Charles P. Noyes, Adviser on Security Council Affairs, United States Mission at the United Nations, June 25, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 144–147, http://history.state.gov/historicaldocuments/frus1950v07/pg_144.

Memorandum of Conversation, by the Assistant Secretary of State for Far Eastern Affairs (Rusk), July 3, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 285–286, http://history.state.gov/historicaldocuments/frus1950v07/pg_285.

Walter H. Waggoner, “Acheson Says U.S. Is Trying to Keep Peiping Out of War,” New York Times, August 31, 1950, http://timesmachine.nytimes.com/timesmachine/1950/08/31/95803685.pdf.


Warren I. Cohen, “The Korean War and Its Consequences,” in The Cambridge History of American Foreign Relations, vol. 7, America in the Age of Soviet Power, 1945–1991, ed. Warren I. Cohen (Cambridge: Cambridge University Press, 1999), 58–80, http://cambridge.org/core/services/aop-cambridge-core/content/view/985AF246A4A8DF9419621F8E885149D9/9781139054683c3_p58-80_CBO.pdf/korean_war_and_its_consequences.pdf.

Bruce Cumings, “A Murderous History of Korea,” London Review of Books, May 18, 2017, http://lrb.co.uk/v39/n10/bruce-cumings/a-murderous-history-of-korea.

Bruce Cumings, “Time to End the Korean War,” Atlantic, February 1997, http://theatlantic.com/magazine/archive/1997/02/time-to-end-the-korean-war/376775.

John P. Glennon, ed., Foreign Relations of the United States, 1950, Korea, Volume VII, (Washington, DC: U.S. Government Printing Office, 1976), http://history.state.gov/historicaldocuments/frus1950v07.

Jacob Heilbrunn, “The 38th Parallel,” New York Times, September 8, 2010, http://nytimes.com/2010/09/12/books/review/Heilbrunn-t.html.

Robert Jervis, “The Impacts of the Korean War on the Cold War,” Journal of Conflict Resolution 24, no. 4 (December 1980): 563–592, http://jstor.org/stable/pdf/173775.pdf?refreqid=search:e7f8072171af6b14e0934b3a19abde1a.  

Donggil Kim and William Stueck, “Did Stalin Lure the United States into the Korean War? New Evidence on the Origins of the Korean War,” North Korea International Documentation Project,  Woodrow Wilson Center for Scholars, June 2008, http://wilsoncenter.org/sites/default/files/NKIDP_eDossier_1_Origins_of_the_Korean_War.pdf.

James I. Matray, “Dean Acheson’s Press Club Speech Reexamined,” Journal of Conflict Studies 22, no. 1 (August 2002), http://journals.lib.unb.ca/index.php/jcs/article/view/366/578.

James I. Matray, “Korea’s Partition: Soviet-American Pursuit of Reunification, 1945–1948,” Parameters, Spring 1998, 139–168, http://ssi.armywarcollege.edu/pubs/parameters/articles/98spring/spr-essa.htm#Matray.

John J. Muccio (U.S. ambassador to Korea, 1949–1952), interview by Jerry N. Hess, February 18, 1971, transcript, Harry S. Truman Presidential Library and Museum, Independence, MO, http://trumanlibrary.org/oralhist/muccio2.htm.

Madison Park, “Why the Korean War Still Matters,” CNN, March 11, 2013, http://cnn.com/2013/03/07/world/asia/korean-war-explainer/index.html.

Jong-yil Ra, “Governing North Korea. Some Afterthoughts on the Autumn of 1950,” Journal of Contemporary History 40, no. 3 (July 2005): 521–546, http://jstor.org/stable/pdf/30036341.pdf?refreqid=excelsior%3A36675c595101b5f45b596363e8318579.

Bruce Riedel, “Catastrophe on the Yalu: America’s Intelligence Failure in Korea,” Brookings Institution, September 13, 2017, http://brookings.edu/blog/order-from-chaos/2017/09/13/catastrophe-on-the-yalu-americas-intelligence-failure-in-korea.

James F. Schnabel, Policy and Direction: The First Year, vol. 3 of United States Army in the Korean War (Washington, DC: Center of Military History, United States Army, 1972), http://history.army.mil/books/P&D.HTM.

Liam Stack, “Korean War: a ‘Forgotten’ Conflict that Shaped the Modern World,” New York Times, January 1, 2018,  http://nytimes.com/2018/01/01/world/asia/korean-war-history.html.

Kathryn Weathersby, “New Russian Documents on the Korean War,” Cold War International History Project Bulletin, 1995: 30–125, http://wilsoncenter.org/sites/default/files/CWIHPBulletin6-7_p2.pdf.

Katheryn Weathersby, “The Korean War Revisited,” Wilson Quarterly 23, no. 2 (Summer 1999): 91–95, http://jstor.org/stable/pdf/40259929.pdf?refreqid=search:e93d0f6bb8b1548e51c5646e4903be96.

Kathryn Weathersby, “To Attack, or Not to Attack? Stalin, Kim Il Sung and the Prelude to War,” Cold War History Project, December 31, 2005, http://upf.org/peace-and-security/northeast-asia-peace-initiative/1755-to-attack-or-not-to-attack-stalin-kim-il-sung-and-the-prelude-to-war.

James Wright, “What We Learned from the Korean War,” Atlantic, July 23, 2013, http://theatlantic.com/international/archive/2013/07/what-we-learned-from-the-korean-war/278016.


Quote Sources


Harry S. Truman, remarks to senators and members of Congress in the Cabinet Room, White House, June 25, 1950, http://trumanlibrary.org/whistlestop/study_collections/korea/large/documents/pdfs/ki-2-40.pdf.



James F. Schnabel, Policy and Direction: The First Year, vol. 3 of United States Army in the Korean War (Washington, DC: Center of Military History, United States Army, 1972), http://history.army.mil/books/P&D.HTM.



Memorandum by the Director of the Office of Northeast Asian Affairs (Allison) to the Assistant Secretary of State for Far Eastern Affairs (Rusk), July 1, 1950, in Foreign Relations of the United States, 1950, Korea, Volume VII, ed. John P. Glennon (Washington, DC: U.S. Government Printing Office, 1976), 272, http://history.state.gov/historicaldocuments/frus1950v07/pg_272.



Barack Obama, “Remarks by the President at 60th Anniversary of the Korean War Armistice,” July 27, 2013, transcript, http://obamawhitehouse.archives.gov/the-press-office/2013/07/27/remarks-president-60th-anniversary-korean-war-armistice.

Students at a Model Diplomacy simulation.
Students at a Model Diplomacy simulation.
Students at a Model Diplomacy simulation.

3.3 Guide to the Memoranda

A major goal of the Model Diplomacy program is to strengthen your ability to write concise, articulate, and persuasive documents that busy colleagues can absorb quickly. In completing this section and Section Four, you will write two memoranda, or memos. These assignments will improve your writing skills and give you a taste of how U.S. foreign policy is conceived, coordinated, and executed.

What is a memorandum?

  • A memo is a formal, succinct written message from one person, department, or organization to another. It is an important form of formal, written communication in the workplace. A memo is generally short, to the point, and free of flowery language and extraneous information. A memo is typically informative or decision-oriented and is formatted in a way that helps readers quickly grasp the main points.
  • In the National Security Council (NSC), memos consider, coordinate, and articulate policy options. They help analyze, evaluate, advocate, and channel those policy options and decisions within the bureaucracy.
  • Memos also function as historical record. Many memos related to NSC discussions and presidential decisions are filed in government archives. Some are later declassified and released to help people understand how policy was devised at a given time in U.S. history. You can access historical examples of memos online. One such resource is maintained by the Federation of American Scientists and offers links to memoranda and directives that various U.S. presidents have issued.

Position Memo 


  • The first memo everyone (except the president) writes is called a position memo. It is written from the perspective of your assigned role. It presents a set of policy options for consideration by the NSC and recommends one of them to the president. The recommendation, or position, outlined in this memo is the one you will present during the role-play. (Keep in mind you may change your position as a result of the role-play discussion.)
  • The position memo will help your fellow NSC members consider the issue efficiently and facilitate decision-making by the president. Equally important, it will help you clarify your understanding of the case by forcing you to identify the essential facts and viable policy options.
  • If you have been assigned a specific role, remember that you are writing from the point of view of the department, agency, or office you represent. Using your institutional position as a lens, you will outline a set of options to address the crisis. Make sure you take into account the pros, cons, and ramifications of each option as it pertains to your role and as it is informed by your reading of the case materials and further research. Also, anticipate critiques of your proposed policy and incorporate your response into the memo. Doing so will help you prepare for the role-play.

Note: If you are assigned the role of president, you will not write a position memo. Instead, you will write a two-page presidential directive, or PD, at the conclusion of the role-play. You will address the PD, which will follow a memo format, to the NSC members and inform them of your final decision regarding the policy option or options to be implemented (see below).

If your teacher has chosen to assign everyone the role of general advisor to the president, you will not need to write the position memo from a particular institutional position. Instead, you will have the flexibility to approach the issue from your own perspective, incorporating a comprehensive assessment of the crisis into your argument.


Position Memo Guidelines

Total length: approximately one thousand words

  • Subject and background (two short paragraphs): Summarize in the first paragraph the significance of the issue in the context of U.S. foreign policy and national security. Identify in the second the central policy question or questions to be decided. Provide just enough information about the crisis so that the reader understands your memo’s purpose and importance; do not attempt to discuss the case in any depth.
  • Objectives (bullet points): Succinctly state your department’s objectives in the current crisis. These can be general national security objectives (such as preventing war) or more specific goals tied to your department’s mission (such as protecting U.S. citizens). They should be important to U.S. national security, directly tied to the case, and feasible. These objectives should guide the policy analysis and recommendation that make up the rest of your memo.
  • Options and analysis (one paragraph for each option): Present and analyze several options for U.S. policy. Discuss their costs, benefits, and resource needs where possible. To illuminate the trade-offs inherent in complex policy decisions, be sure to acknowledge the weaknesses or disadvantages of each proposed option. No option is likely to be perfect.
  • Recommendation and justification (several paragraphs): Identify your preferred policy option or options and describe how you think it or they could be carried out. Explain your reasoning, keeping in mind that you aim to convince the president to follow your recommendation. Addressing the weaknesses or disadvantages you identified in the options and analysis section can help strengthen your argument.

Click here to see a sample position memo.

Presidential Directive


The format of the presidential directive is simpler than that of a position memo. A directive contains a record of the policy option or options that the president has chosen as well as the accompanying orders to various parts of the government with details on how to carry out these decisions.

  • Start with a short paragraph describing the purpose of the memo. Everyone you are writing to was in the NSC meeting, so only brief context is needed.
  • Explain in numbered paragraphs the decisions you have made, why you have made them, and any details regarding how you want the decisions carried out.
  • Explain the communications strategy for the decision, considering both relevant foreign governments and the public. Also, consider that you may wish to keep certain elements of the decision secret from the public.
  • Include any additional details before you sign.
  • Be sure to include all the information necessary for NSC members to understand and carry out your intentions.

Click here  to see a sample presidential directive.

Students at a Model Diplomacy simulation.
Students at a Model Diplomacy simulation.
Students at a Model Diplomacy simulation.

3.4 Guide to the Role-play

During the simulated NSC meeting, you will meet to debate and discuss U.S. policy options in response to the issues outlined in the case. Consistent with the NSC’s mission to advise the president, you should raise the issues that are most important for the president to consider. This will enable him or her to make the most informed decision on policy options. Though you may or may not agree with this decision, your responsibility as an NSC member is to provide the best possible analysis and advice from the perspective of your role.

Role-play Guidelines

  1. Stay in your role at all times.
  2. Follow the general protocol for speaking.
    1. Signaling to Speak

      1. The National Security Advisor (NSA) will administer the meeting and should decide on a speaking order. Wait to be called on by the NSA.
      2. If you would like to speak out of turn, signal to the NSA, perhaps by raising a hand or a placard, and wait until the NSA calls on you.
    2. Form of Speech
      1. Address the president as Mr. or Madam President and your fellow NSC members in the same fashion (for example, Madam Secretary).
      2. Do not exceed predetermined time limits. If you exceed these limits, the NSA will cut you off.
      3. Frame your comments with a purpose and stay on topic. Remember that you must advise the president so that he or she can reach a decision on a precise policy question.
    3. Listening
      1. Take notes while others are speaking.
      2. Refrain from whispering or conducting side conversations.
      3. Applause and booing are not appropriate. Your words will be the most effective tool to indicate agreement or disagreement.


Role-play Tips

  • There is no right or wrong way to participate in a role-play, but the better prepared you are, the more likely you will be able to advance a position effectively, and the more you and your classmates will get out of the experience.
  • Be patient during the role-play. Do not hold back from sharing your perspective, but be sure to give others a chance to do the same.
  • Where there are competing interests, make the judgment calls that you would make if you were a government official, as informed by your earlier consideration of potential trade-offs. Ensure that the consequences of various decisions are carefully weighed.
  • Where appropriate, find common ground with other members of the NSC during the role-play. With whom might you work in advocating your proposed policies? You may find that combining several policy ideas into a new proposal with broader support is an effective strategy if the debate is at an impasse.
  • Think critically about the strengths and weaknesses of your approach as the discussion continues. It is important to subject your own arguments to the same scrutiny that you apply to those of your fellow students. Rethink your arguments as appropriate to take into account the feedback and counterarguments that other NSC members present.
  • You cannot win or lose the role-play. Instead, you should aim to offer a well-reasoned articulation of your position while making concessions and adjustments where you believe they are warranted.
Line Item
2 to 3 minutes per participant
  1. Present initial positions to the president.
  2. Investigate the nuances of the positions through questioning.
  3. Clarify the central questions to be debated.
Procedural Notes

Each participant presents his or her position statement. If time permits, the president may ask questions to understand each NSC member’s position and bring out the essential questions he or she wishes to debate.

30 to 60 seconds per participant
  1. Clarify the obstacles, risks, opportunities, and threats.
  2. Evaluate the various positions on their merits.
Procedural Notes

This is the debate portion of the role-play, when participants can defend their recommendations against others’ and identify potential areas of compromise or agreement.

30 to 60 seconds per participant
  1. Narrow the options to a few comprehensive and well- focused strategies that the president prefers.
  2. Provide the president with clear recommendations (from NSC members), perhaps as a consensus or through a vote.
  3. Arrive at a final presidential decision 
Procedural Notes

This round should start with the president’s stating one to three preferred options to be fleshed out.

Wrap Up Sections
Obama, Xi Jinping, and Ban Ki Moon.
The UN Security Council

4.1 The Debrief

After the debate and deliberation close, the president will announce his or her decision, to be later finalized in the form of a written presidential directive (PD). If time permits, you will participate in a debrief following the president’s announcement. 

Be active in this debrief. The role-play might seem to be the most challenging part of the experience, but the debrief is equally important. It will reinforce what you learned during the role-play exercise and refine your analytical skills. It will also force you to step out of your role and to view the case from a personal perspective. You will have the opportunity to discuss any challenges you encountered and how you felt about the final presidential decision. The debrief will close with a reflection on the complexities and challenges of crafting foreign policy. This should help clarify your understanding of what you learned and answer any lingering questions. This exercise will also assist you in completing your final assignment, the policy review memo.  

Obama, Xi Jinping, and Ban Ki Moon.
The UN Security Council

4.2 What Actually Happened 

In September 1950, the National Security Council issued Report 81/1, entitled “United States Courses of Action with Respect to Korea,” which outlined the council’s official recommendation on the question of whether to invade North Korea. It concluded that “the United Nations forces have a legal basis for conducting operations north of the 38th parallel” and that

the UN Commander should be authorized to conduct military operations, including amphibious and airborne landings or ground operations in pursuance of a roll-back, north of the 38th parallel for the purpose of destroying the North Korean forces, provided that at the time of such operations there has been no entry into North Korea by major Soviet or Chinese Communist forces, no announcement of intended entry, nor a threat to counter our operations militarily in North Korea.

On September 15, UN forces landed at Inchon, backed by naval and air bombardment. The landing was an extraordinary success, stunning the North Korean forces and forcing them into withdrawal. By the end of September, South Korean and UN troops had recaptured Seoul and officially restored the South Korean government under Syngman Rhee.  On October 1, General Douglas MacArthur officially demanded North Korea’s surrender. Receiving no reply, he authorized South Korean forces to advance across the border, with UN forces following closely behind once they received authorization. This authorization came on October 7, with a UN General Assembly resolution calling on UN forces to take “all appropriate steps . . . to ensure conditions of stability throughout Korea.”

Within the first few weeks of their attack, UN forces moved rapidly northward. Facing little resistance from the retreating North Korean soldiers, UN and South Korean forces advanced swiftly and captured Pyongyang on October 19. But things did not continue as smoothly. On October 25, Chinese forces began operations against South Korean forces. It would be more than a month before the United States acknowledged that China was mounting a full-scale intervention in Korea. By then, UN forces were being pushed south, their gains since crossing the thirty-eighth parallel quickly reversed. Seoul fell for the second time in January 1951; three months later, Truman fired MacArthur.

After a series of bloody attacks and counterattacks, UN and Chinese forces met at the thirty-eighth parallel in a stalemate in the spring of 1951. For the next two years of fighting, they only made moderate gains and losses of ground around the parallel. On July 27, 1953, China, North Korea, and the UN Command signed an armistice, bringing an end to the fighting. Though the agreement was meant to establish a ceasefire “until a final peaceful settlement is achieved,” no settlement was ever agreed on. To this day, the two Koreas are still officially at war, and the thirty-eighth parallel has become the most heavily militarized border in the world.

The effects of the war were acutely felt on the peninsula, where more than two million were killed—as many as 70 percent of them civilians. The United States dropped more explosives on North Korea during the three-year conflict than in the entire Pacific theater during World War II, destroying an estimated 85 percent of buildings in the country.

How was the decision made? 

The burgeoning Cold War was the most important factor in Truman’s deliberations over crossing the thirty-eighth parallel. The president sought to make a decision that would strengthen the United States’ position in relation to the Soviet Union, and, to a lesser extent, Communist China. Ultimately, as scholar Bruce Cumings notes, “nearly all of Truman’s high advisers decided that the chance had come not only to contain Communist aggression, but to roll it back.”

Compounding this were assessments by the intelligence community that the risk of a Soviet or Chinese response was low. The widespread belief was that while there had been indications of Chinese intent to intervene, these indications had likely been bluffs. Secretary of State Dean Acheson summed up these feelings in a CBS interview in September 1950, calling the prospect of a Chinese intervention “sheer madness.”

Moreover, MacArthur was strongly in favor of crossing the parallel, saying in July, “I may need to occupy all of North Korea.” The Joint Chiefs of Staff (JCS) held a similar view, writing to the secretary of defense in September that “after the strength of the North Korean forces has been broken . . . subsequently operations must take place both north and south of the 38th parallel.”

On September 11, 1950, Truman approved a National Security Council policy statement recommending that a course of action in Korea “would be influenced by three factors: action by the Soviet Union and the Chinese Communists, consultation with friendly members of the United Nations, and the risk of general war.” On September 15, the day of the Inchon landing, Truman approved a JCS directive based on this policy statement, which authorized military operations beyond the thirty-eighth parallel if there was no indication or threat of entry of Soviet or Chinese Communist forces. On September 27, following the immense success of the Inchon landing, the JCS sent new instructions to MacArthur. His military objective was now “the destruction of the North Korean Armed Forces,” for which he was authorized to conduct military operations north of the thirty-eighth parallel.  

What did the decision mean?

Though largely forgotten by—or unknown to— many in the West, the Korean War’s effects have shaped geopolitics and reverberated through history. The war cemented alliances and rivalries that endure today, ushered in policies that would characterize many years of the Cold War, and finalized the thirty-eighth parallel as an enduring dividing line on the Korean Peninsula.

  1. Solidification of Alliances and Rivalries

The Soviet Union and China continued to economically and politically support North Korea throughout the Cold War, as the United States did South Korea. Two months after the armistice was signed in 1953, the latter pair cemented their alliance with the Mutual Defense Treaty Between the United States and the Republic of Korea, establishing a powerful military alliance underwritten by American nuclear weapons.

Despite the collapse of the Soviet Union in 1991, these relationships are still largely in place today. Today, South Korea hosts over twenty thousand American troops, and North Korea maintains relatively close, though sometimes fraught, relationships with Russia and China.

  1. Cold War Policies

The Korean conflict heralded many of the hallmarks of U.S. foreign policy during the Cold War. One of those was the concept of limited war—a war in which limited resources, forces, and tactics are used in service of goals significantly short of total destruction of the enemy. Because the United States and the Soviet Union were both wary of triggering a general—­and quite possibly nuclear—war, they became involved in limited proxy conflicts during the Cold War. The Korean War would be followed by similar conflicts in Vietnam and Afghanistan. Hand in hand with this policy was the doctrine of containment, which advocated for “containing” the spread of communism within national borders (and which had served as Truman’s primary rationale for entering the Korean War). In many ways, the Korean War became a blueprint for how the Cold War would be fought.

  1. An Enduring Division

Perhaps the most significant legacy of the Korean War is the enduring division of the Korean Peninsula. Since its establishment as an arbitrary administrative boundary in 1945, the thirty-eighth parallel has remained the dividing line between North and South Korea.

Since the armistice was declared, relations between North and South Korea have ranged from conciliatory to combative. Particularly in the last few decades, the peninsula has seen a few near brushes with war. In 2006, after years of development, North Korea ratcheted up the tension by testing its first nuclear weapon. (South Korea remains under the U.S. nuclear umbrella, meaning that the United States has pledged to defend South Korea from any nuclear attack). According to scholar Bruce Cumings, North Korea’s generals “are still fighting the war. For them it has never ended.”

Was it a good idea? 

Many accounts of the Korean War frame the decision to cross the thirty-eighth parallel as a mistake. Bruce Riedel of the Brookings Institution calls it “by far the worst military debacle the U.S. armed forces suffered in the entire twentieth century” and a “catastrophic intelligence failure . . . that cost the lives of thousands of Americans.” Similarly, historian Warren Cohen writes that the Truman administration, “in its moment of triumph . . . succumbed to one of the most treacherous temptations confronting any victor, the temptation to expand war aims.”

Journalist and U.S.-China relations scholar John Pomfret argues that the United States’ biggest mistake was in underestimating the potential for Chinese involvement; he reports that General Matthew Ridgeway, who had led operations in Europe during World War II, noted that General MacArthur “‘simply closed his ears’ to the growing presence of Chinese troops in Korea.” Similarly, scholar Robert Farley argues that “the initial Chinese victories in late fall of 1950 resulted from a colossal intelligence failure on the part of the United States. These failures ran the gamut from political, to strategic, to operational, to tactical. . . . The United States also misunderstood the complex relationship between Moscow, Beijing, and Pyongyang, treating the group as unitary actor without appreciating the serious political differences between the countries.”

Other scholars, however, are more sympathetic to the decision’s historical context. Scott A. Snyder of the Council on Foreign Relations argues that “it would have been difficult to imagine that any commander . . . would have made the decision to simply halt in the face of what looked like an open field up to the China and North Korea border.” Historian William Stueck also defends the decision, arguing that by the time the threat of Chinese intervention became credible, the decision to advance had already gained too much momentum: “to delay action would have disappointed expectations in the United States in the midst of a congressional election campaign, would have compromised a clear military advantage, and would have constituted an apparent loss of nerve in the face of Communist pressure tactics.”

In sum, scholars debate whether the decision to cross the thirty-eighth parallel represents a failure to assess intelligence and understand Chinese and Soviet motivations or a calculated decision to consolidate victory and demonstrate commitment to broader foreign policy goals. But the legacy of the war remains certain: the lasting division between North and South Korea has remained a critical foreign policy challenge to this day.

Obama, Xi Jinping, and Ban Ki Moon.
The UN Security Council

4.3 Reflecting on the Experience

The following questions are proposed to guide the discussion in the in-class debrief. This is not an exhaustive list and may vary depending on how your role-play exercise unfolded.  If your class does not hold a debrief, these questions will nonetheless help you reflect on the role-play and write your policy review memo: 

  • Which issues received adequate attention during the role-play? Which, if any, received excessive attention or were left unresolved?
  • Did the group consider long-term strategic concerns, or was it able to focus only on the immediate issue and the short-term implications of policy options?
  • Which U.S. interests did the group or the president prioritize in the PD and why? Were you comfortable with this prioritization?
  • Did time constraints affect the discussion and influence the policymaking process?
  • Compare the events and ultimate policy decision in the role-play to the events as they occurred in the past. How accurately did the simulation replicate the past? How did it differ, and why?
  • Can you apply the lessons from this case study to current events in international affairs? If so, how?
  • Knowing what we do now about the historical events that followed the Decision Point, do you think the policy decision selected by the group was a good choice? What techniques did you use to convince others that your policy position was the best option? What were successful strategies employed by others?
  • What were the most significant challenges to your position? Did any make you rethink or adjust your position?
  • Did your points cause anyone else to change his or her arguments or position?
  • Were your position and points affected by what you knew about historical events as they actually occurred? If so, how?
  • What political, economic, and other issues arose that you had not previously considered?
  • How did the simulation change your perspective on foreign policy decision-making?
  • Did the simulation change your perspective on this historical issue? If so, how?
  • If you could go back, what would you have done differently in presenting and advocating your point of view?
Obama, Xi Jinping, and Ban Ki Moon.
The UN Security Council

4.4 Policy Review Memo

The policy review memo is your final assignment in the Model Diplomacy simulation. In the debrief discussion after the role-play, you and your classmates went beyond the role you played and thought about the issue from a variety of perspectives. Now that the National Security Council discussion and debrief are behind you, you can consider whether you personally support your recommended policy given the full spectrum of arguments and considerations that arose. Shedding your institutional role and writing from a personal point of view, you will craft a policy review memo that outlines and reflects on the policy options discussed, incorporating and critiquing the president’s decision where appropriate.

If you played the role of president in the simulation, your memo should still reflect your personal opinion. You can comment on the course of action you ordered as president, further justify it, write more extensively on the options you dismissed, or suggest and support alternate options.

No matter which role you played originally, take into account all you have learned. Your instructor will want to see whether and how your understanding of the issue and of the policymaking process has evolved from that expressed in your position memo.

As for the position memo, a sample policy review memo is provided for your reference.

Policy Review Memo Guidelines

  • Subject (one short paragraph): Offer a brief statement about the significance of the issue as it relates to U.S. foreign policy and national security. Provide just enough information about the crisis so that the reader can understand the purpose and importance of your memo. Be sure to include an initial statement of whether you agree or disagree with the president’s decision.
  • Options and analysis (one paragraph per option): Present and analyze the options discussed during the debate, deliberation, or debrief. Discuss their drawbacks, benefits, and resource needs. Be sure to acknowledge any weaknesses or disadvantages of the proposed options.
  • Recommendation and justification (several paragraphs): Identify and explain your preferred policy option or options in more detail. Here, you can explain why you personally favor one or more of the recommendations that you initially presented or the president chose, or different options entirely. If you choose to support the options you presented in your position memo, make sure to justify why you feel yours is still the best position.
  • Reflection (one to two paragraphs): Discuss how your position and the presidential directive are similar; if they are not, discuss how they are different. Use this section to give your thoughts on what the president should have included in his directive, or what you would have done differently. Remember, this is from your point of view; you are no longer advocating on behalf of a department or agency.

Click here to see a full example of a policy review memo.