May be a useful reference for this studying this subject. An interesting historical review.
U.S. Global Defense
Today, in response to changes in the political, fiscal, and strategic environments, the United States is revising its global defense posture. The Department of Defense has announced a number of initiatives that are a part of its rebalancing toward Asia, while, at the same time, maintaining a significant presence in Southwest Asia, even as U.S. forces are drawn down in Afghanistan. As these plans move forward, it is important to recognize that America’s overseas military presence, as it currently exists in terms of scope and scale, is largely a legacy of the Cold War and that, over the past two centuries, the United States repeatedly adjusted its posture in response to the emergence of new types of threats, technological innovations, and the availability of overseas bases. Understanding past U.S. postures, what they looked like, why they were implemented, and why they changed can provide important insights for policymakers as they look to modify today’s global defense posture in the coming years.