Why has the United States, with its long-standing Liberal tradition, come to embrace the illiberal policies it has in recent years? The conventional wisdom is that al-Qaida's attacks on the United States on September 11, 2001, and the subsequent war on terrorism have made America less Liberal. The logic of this argument is straightforward: interstate war has historically undermined domestic liberties, and the war on terrorism is causing the United States to follow this well-worn path. This explanation confronts a puzzle, however: illiberal U.S. policies—including the pursuit of global hegemony, launching of a preventive war, imposition of restrictions on civil liberties in the name of national security, and support for torture under certain circumstances—manifested themselves even before the September 11 terrorist attacks and were embraced across the political spectrum. Indeed, it is precisely American Liberalism that makes the United States so illiberal today. Under certain circumstances, Liberalism itself impels Americans to spread their values around the world and leads them to see the war on terrorism as a particularly deadly type of conflict that can be won only by employing illiberal tactics.