The United States confronts challenges from revisionist great powers such as China and Russia, aggressive rogue states such as Iran and North Korea, and international terrorist organizations such as al-Qaeda and the Islamic State. At the same time, constant-dollar defense spending fell from $768 billion in 2010 to $595 billion in 2015, the fastest drawdown - in percentage terms - since the Korean War. The result has been a creeping crisis of American military primacy, as the margin of superiority to which the United States has become accustomed has diminished, and a growing gap between U.S. commitments and capabilities has emerged. Closing that gap will require a significant, sustained defense buildup in the years to come.
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