Despite their disagreements, proponents of deep engagement and offshore balancing share an optimistic but unrealistic assessment of U.S. military power. In particular, both sides in the debate over U.S. grand strategy underestimate the potential consequences of China’s military modernization. China’s antiaccess/area denial strategy and conventional precision-strike capabilities are already undermining the United States’ ability to prevent local conflicts, protect longtime allies, and preserve freedom of the commons in East Asia. Whether the United States intends to uphold the status quo when threats emerge or adopt a wait-and-see approach to regional conflicts, it will need to adapt its military for power projection operations in much less permissive environments than it has become accustomed to during the unipolar era. These adaptations include developing air and undersea platforms that can survive inside denial zones, forward bases that are better able to withstand attacks, and satellite and cyberspace networks that are less vulnerable to disruption.