As the only superpower in the international system，the United States uses its force and takes military intervention abroad more often than any other state. Researchers usually argue that the United States has strong unilateral incentives to make decisions and implement military intervention—the US is prone to use or threaten to use the force frequently and obstinately，ignoring the United Nations and international law. An investigation of major US military interventions in the post-Cold War era shows that the United States has often relied on temporary coalitions rather than persistent alliances in military and stability operations，although its decisions to use force are less constrained by the international community. The United States has motivations to recruit multinational military coalitions，such as avoiding the dilemma of collective action，reducing the burden of intervention and acclaiming the legitimacy of their interventions. Military coalitions have clearly-defined missions and flexible means，which provide convenience for the United States to take a leading role in military interventions.