Americans have struggled to reconcile capitalism and war. Over three centuries of history, they have grappled with fundamental tensions between capitalism and security. The combination of war and capitalism often created disruptions and deep inequities that ordinary Americans and their leaders decided must be moderated for the sake of a more successful and politically sustainable war effort. For much of the nation’s history, capitalism was understood to be an insufficient provider of security; the U.S. military economy was semi-socialized, in both peacetime and wartime. But as the record of recent decades has highlighted, Americans have not experienced an ever-higher ratcheting of regulation and socialism, with each new war, over the long run. Rather, the historical record suggests that many postwar demobilizations served to reinforce capitalism. For the nation’s entire history, struggles over the economics of war and national security have been important parts of U.S. political development. This will continue to be the case in the current century, as Americans battle over economic policy and fight new wars, domestically and abroad.