Grand strategic choices are among the most important decisions senior leaders must make. Getting grand strategy right is fundamental to success in the Global War on Terrorism. This monograph assesses the grand strategic choices presented to the United States since 2001, by evaluating their ability to serve our basic national security interests in a post-September 11, 2001 (9/11), world, and by identifying implications for American policy in the coming years. The author, Dr. Stephen Biddle, argues that some of the most important of these choices have yet to be made. Policymakers must arrive at a clear definition of the enemy and the aim in the War on Terrorism; to date, American policy has combined ambitious public statements with ambiguity on critical particulars. The ongoing insurgency in Iraq is increasing the costs of grand strategic ambiguity to the point where fundamental choices can no longer be deferred.