The election of President Obama presents an opportunity to assess, and, if necessary, adjust U.S. military policies on when war may be waged. President Bush asserted the Bush Doctrine of using preemptive force against putative enemies before they have the capability to attack the United States. After the wars in Iraq and Afghanistan, the time is ripe to evaluate whether the United States should continue the Bush Doctrine. Through statistical regressions of all attacks by or on the United States over sixty years, as well as field interviews of the Taliban, Islamic leaders, and foreign officials in Pakistan and Iran, this Article demonstrates that U.S. military action does not observably reduce aggregate attacks against the United States, and is likely to increase hostility against it. When the U.S. military responds to an actual attack, these considerations are secondary to preventing certain and immediate death and destruction that would occur if the United States did not act. Where there is clear evidence that a putative enemy will launch a devastating attack against the United States should the United States fail to preempt the attack with force, these considerations are also secondary. However, absent such clear and convincing evidence, the indeterminate effects of U.S. military action on aggregate national security and the risk of stoking global animus should tilt the balance against military preemption. This Article recommends that before President Obama—or any future U.S. President—authorizes preemptive military force, he or she should require U.S. policy makers to meet a high burden of proof that a putative enemy will attack or injure the United States if the United States does not strike first. As an alternative to preemptive attacks, this Article recommends five strategies that might better promote U.S. security.