Who actually decides when the United States goes to war—Congress or the president? Richard Epstein traces the Constitution’s original division of war powers from 1789 to the present and explain how practice, politics, and modern warfare have steadily shifted authority toward the presidency. Along the way, they explore declarations of war that never happen, authorizations that never expire, emergency actions that become routine, and why Congress so often prefers not to decide at all. Professor Epstein argues that America now operates under two constitutions—the one we wrote and the one we live with.