a strategy used to discourage an enemy from attacking by instilling a fear of retaliation. Scholars generally consider an effective deterrent to rely on capability and will, that is the means to retaliate and the intention to do so. Deterrence was the foundation of U.S. and NATO strategy toward the Soviet Union during the Cold War. One variant is extended deterrence, in which a state threatens retaliation to prevent attacks not on itself but on its allies. The United States has long used extended deterrence to protect NATO members and other allies. In this way, the United States is also offering to these allies what is called a security guarantee.