Despite the ubiquity of the term “alliance of convenience,” the dynamics of these especially tenuous alliances have not been systematically explored by scholars or policymakers. An alliance of convenience is the initiation of security cooperation between ideological and geopolitical adversaries in response to an overarching third-party threat; they are conceptually different from other types of alliances. Neorealist, two-level games, and neoclassical realist theories all seek to explain the outcome of intra-alliance bargaining between the United States and allies of convenience since 1945. Neorealism and two-level games theories broadly predict successful U.S. bargaining because of the United States' favorable position in the international system and the relatively tight constraints on executive power in the United States, respectively. By contrast, neoclassical realism predicts that tight constraints on executive power in the United States should have led the foreign policy executive to bargain unsuccessfully with allies of convenience. In the case of the U.S. alliance of convenience with Iraq during the 1980–88 Iran-Iraq War, neoclassical realism best explains the outcome of U.S. bargaining with Iraq. This case has implications for other U.S. bargaining efforts.