Under what conditions and for what reasons do American leaders seek the endorsement of relevant international organizations (IOs) such as the UN or NATO for prospective military interventions? My central hypothesis is that U.S. government efforts to obtain IO approval for prospective interventions are frequently the result of significant bureaucratic deliberations and bargaining between hawkish policy leaders who emphasize the likely positive payoffs of a prompt use of force, on the one side, and skeptical officials--with the top military brass and war veterans in senior policy positions at the forefront--who highlight its potential downsides and long-term costs, on the other. The military leaders--the chairman and vice chairman of the Joint Chiefs of Staff (JCS), the regional combatant commanders, and senior planners on the Joint Staff in Washington--are generally skeptical of humanitarian and other "idealist" interventions that aim to change the domestic politics of foreign countries; they naturally tend to consider all the potential downsides of intervention, given their operational focus; and they usually worry more than activist civilian policy officials about public and congressional support for protracted engagements. Assuming that the military leaders are not merely stooges of the civilian leadership, they are at first likely to altogether resist a prospective intervention, when they believe that no vital American interests are at stake and fear an open-ended deployment of U.S. troops. Given the military's professional expertise and their standing in American society, they come close to holding a de facto veto over prospective interventions they clearly oppose. I hypothesize that confronted with such great initial reluctance or opposition on the part of the military brass, civilian advocates of intervention from other government agencies will seek inter alia to obtain an advance endorsement from relevant IOs, so as to lock in international support and thereby reassure the military and their bureaucratic allies that the long-term costs to the United States in terms of postwar peacekeeping and stabilization will be limited. That, in turn, can be expected to help forge a winning bureaucratic coalition in Washington and persuade the president to authorize military action. United States multilateralism for military interventions is thus often a genuine policy resultant--the outcome of sustained bureaucratic deliberations and bargaining--and it may not actually reflect the initial preferences of any particular government agency or senior official