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Ukrainian Soldiers operating Anti-Aircraft Missile System

Trusting Security Assurances

This pop-up case is part of the series: Russia’s War in Ukraine


Ukraine gave up its nuclear arsenal in exchange for security assurances. Yet those assurances failed to prevent a Russian invasion, raising questions for other would-be nuclear powers about the reliability of outside security assurances and whether pursuing a nuclear program provides the best guarantee of their future security. How should a hypothetical country under threat decide its nuclear future?

Students will understand that countries act in numerous ways to convince other governments not to develop nuclear weapons of their own, including by offering security assurances to ease their fears of an outside attack. 

Students will understand that if countries feel they are unable to rely on outside assurances for their security, they could be driven to develop nuclear weapons to increase their own protection.


The Situation

Nuclear weapons can offer considerable security to countries that possess them; attacking a country that has nuclear weapons bears a far greater risk than attacking a country that lacks them. Yet most countries agree that more nuclear weapons in the world means a higher likelihood that one will eventually be used, with catastrophic consequences. Given this risk, governments worldwide have worked to limit the proliferation of nuclear weapons. Diplomatic efforts, such as the Nuclear Nonproliferation Treaty (NPT), have secured agreements from member countries to either reduce the number of nuclear arms they possess or to not develop them in the first place. 

The NPT has strengthened global norms against developing nuclear weapons. Yet the agreement is voluntary. Countries that fear for their security or wish to exert greater geopolitical power can exit the NPT and pursue a nuclear weapons program, as North Korea did in 2003. Doing so can result in international isolation or coercive action, such as sanctions or even covert attacks. However, some countries could feel so threatened that they are willing to risk those consequences. In these cases, major powers can ease a country’s fears by offering security assurances—commitments that they will not attack the country or will help defend it from attack—if that country gives up its nuclear ambitions. For instance, the United States (a nuclear-armed country) maintains a so-called nuclear umbrella by providing its nonnuclear allies with binding defense guarantees that reduce their incentive to develop their own deterrents.

The combination of convincing countries they are safe without nuclear weapons and threatening penalties for those that pursue them has prompted numerous governments to abandon their nuclear programs. However, recent events could change that calculus. As harsh as the penalties are, no country has faced direct military action over its nuclear development. Moreover, several leaders have abandoned their nuclear programs only to come under threat later. Facing sanctions and international isolation, Iraq dismantled its nuclear program in the 1990s only to face a U.S.-led invasion in 2003. Similarly, Libya agreed to disarm in 2003 and faced a civil war and a North Atlantic Treaty Organization–led intervention less than a decade later. Most recently in the news, Ukraine relinquished its sizable nuclear arsenal in 1994 in exchange for security assurances from the United States, Russia, and the United Kingdom. Those assurances were ineffective: in 2014 and 2022, Russia invaded Ukraine. The United States, although aiding Ukraine with weapons and funds, has stopped short of direct military intervention, in part over reluctance to enter conflict with a nuclear-armed Russia. The invasion underscores both that nuclear-armed countries can act with a degree of impunity and that security assurances for nonnuclear countries are only as strong as their provider’s willingness and ability to follow through. Countries looking on could therefore conclude that they cannot trust outside assurances for their security and that developing a nuclear program, or at least building the capacity to do so quickly, could be more worth the risks than they previously thought.

Decision Point

Schirmland occupies a geopolitically insecure position. Raketburg, the country’s nearest neighbor and a nuclear-armed power, has intermittently made threats against it. Although Schirmlanders explored developing a nuclear program to deter potential aggression, the country disavowed any nuclear ambitions in exchange for assurances that the United States, a close military partner, would defend Schirmland if it were attacked. However, Russia’s invasion of Ukraine has driven Schirmlanders to reconsider how strongly they can rely on U.S. assurances to safeguard their country and whether developing their own nuclear deterrent could provide a stronger guarantee. Schirmland’s president has called a cabinet meeting to decide whether the country should continue to trust in U.S. security assurances or chart a new course and develop nuclear weapons. As they deliberate, cabinet members will need to weigh the risks to their security against the consequences of breaking their existing nuclear commitments.

Cabinet members should consider the following options:

  • Develop nuclear weapons. This would provide Schirmland with a strong deterrent against aggression and eliminate the need to rely on outside assurances for security. However, developing a nuclear weapons program could result in widespread international condemnation and isolation. It would further take time, potentially years, during which other countries could aggressively sanction Schirmland—or even take military action—to derail its nuclear development.

  • Start creating a nuclear weapon but stop short of finishing it. Being able to produce a nuclear weapon within mere months could grant some of the benefits of a nuclear deterrent without risking the worst consequences. However, even if Schirmland avoids violating nuclear commitments, skirting the line of the NPT could be seen as turning away from reliance on U.S. security cooperation. This could sour relations with the United States, making their security assurances even less reliable, while leaving Schirmland exposed to an attack.

  • Continue to rely on U.S. security assurances as a deterrent. This option avoids all consequences of nuclear development but does little to strengthen Schirmland’s confidence in its security. 

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