The credibility of American deterrence rests on a simple foundation. America prevents wars by convincing its adversaries they cannot win. Secretary of Defense Jim Mattis said it succinctly: Deterrence is achieved when the enemy decides, “Not today. You, militarily, cannot win it, so don’t even try it.” Currently, in the Indo-Pacific, that foundation of deterrence is crumbling as an increasingly aggressive China continues its comprehensive military modernization.