The United States has long-defined the free flow of Persian Gulf oil as a key component of its grand strategy. Since the late 1970s, U.S. military force has increasingly become the instrument for achieving this end. The American objective of ensuring the flow of Persian Gulf oil, by force if necessary, has rarely been questioned by scholars or policymakers since the Gulf became the site of U.S. military deployments. It is time to reexamine the U.S. military commitment to keeping Gulf oil flowing. Quite dramatic changes have occurred in world oil markets, the regional balance of power, and the limits of US defense budgets. This opens up the possibility that the United States should significantly revise its policy toward the Persian Gulf--both in terms of how it defines its strategic interests in the region, and the means it uses to pursue them. This volume brings together scholars of international relations and US foreign policy to examine the history and effects of the US presence in the Gulf and to weigh the costs and benefits of either keeping US forces in the region or pulling back.