Republicans and Democrats disagree today on many issues, but they are united in their resolve that the United States must remain the world’s greatest military power. This bipartisan commitment to maintaining American supremacy has become a political signature of our times. In its most benign form, the consensus finds expression in extravagant and unremitting displays of affection for those who wear the uniform. Considerably less benign is a pronounced enthusiasm for putting our soldiers to work “keeping America safe.” This tendency finds the United States more or less permanently engaged in hostilities abroad, even as presidents from both parties…