This article explores the United States' recognition of the doctrine of command responsibility. The doctrine has been invoked by those alleging that President Trump’s pardons of U.S. personnel convicted or accused of war crimes could amount to war crimes themselves. The article focuses on a commander’s duty to punish war crimes by his subordinates. It examines the United States’ past recognition of the duty to punish as an element of command responsibility under the law of war. The principle that a commander has an obligation to punish war crimes by his subordinates is not a progressive development of the law promoted by the advocacy community. Instead, the duty to punish stands out as an ancient legal norm interwoven into the domestic law of the United States and which the United States has incorporated into international legal instruments. The lesson from this history is clear, if not always appreciated: commanders who fail to punish their subordinates for war crimes may themselves be war criminals.