Book excerpt: The United States and other members of the international community are striving to convince North Korea, Iran, and other states to forgo the development of nuclear weapons. If they do not succeed, the consequences for U.S. and allied security could be profound. This research brief describes a RAND Project Air Force Study on nuclear-armed regional adversaries, which encompasses an examination of the historical record, evaluations of the strategies and statements of potential nuclear-armed regional adversaries, and politico-military gaming. This analysis suggests that future U.S. policy makers and commanders will need to develop and field capabilities that can prevent (rather than simply deter) the enemy's use of nuclear weapons.