The current U.S. global defense posture that is, the location and primary operational orientation of the nation s military personnel and the military facilities that its troops have access to is under increasing pressure from a number of sources, including budgetary constraints, precision-guided weapons that reduce the survivability of forward bases, and host-nation opposition to a U.S. military presence. These debates over the shape of the U.S. overseas military presence are not without precedent. As policymakers today evaluate the U.S. forward military presence, it is important that they understand how and why the U.S. global posture has changed. This monograph aims to describe the evolution of the U.S. global defense posture from 1783 to the present and to explain how the United States has grown from a relatively weak and insular regional power that was primarily concerned with territorial defense into the preeminent global power, with an expansive system of overseas bases and forward-deployed forces that enable it to conduct expeditionary operations around the globe. Moreover, this historical overview has important implications for current policy and future efforts to develop a U.S. military strategy, in particular, the scope, size, and type of military presence overseas. As new and unpredictable threats emerge, alliance relationships are revised, and resources decline, past efforts at dealing with similar problems may yield important lessons for future decisions.