Successful coercion should be relatively simple for the United States. Since the demise of the Soviet Union, the United States is without rivals in military might, political influence, or economic strength. Yet despite the lopsided US edge in raw power, regional foes persist in defying the threats and ultimatums brought by the United States and its allies. This book examines why some attempts to strong-arm an adversary work while others do not. It explores how coercion today differs from coercion during the Cold War. It describes the constraints on the United States emanating from the need to work within coalitions and the restrictions imposed by domestic politics, and it assesses the special challenges likely to arise when an adversary is a non-state actor or when the use of weapons of mass destruction is possible.