This book questions when, why, and how it is just for a people to go to war, or to refrain from warring, in a post-9/11 world. To do so, it explores Just War Theory (JWT) in relationship to recent American accounts of the experience of war. The book analyses the jus ad bellum criteria of just war—right intention, legitimate authority, just cause, probability of success, and last resort—before exploring jus in bello, or the law that governs the way in which warfare is conducted. By combining just-war ethics and sustained explorations of major works of twentieth and twenty-first century American war writing, this study offers the first book-length reflection on how JWT and literary studies can inform one another fruitfully.