What determines when states adopt war taxes to finance the cost of conflict? We address this question with a study of war taxes in the United States between 1789 and 2010. Using logit estimation of the determinants of war taxes, an analysis of roll-call votes on war tax legislation, and a historical case study of the Civil War, we provide evidence that partisan fiscal differences account for whether the United States finances its conflicts through war taxes or opts for alternatives such as borrowing or expanding the money supply. Because the fiscal policies implemented to raise the revenues for war have considerable and often enduring redistributive impacts, war finance—in particular, war taxation—becomes a high-stakes political opportunity to advance the fiscal interests of core constituencies. Insofar as the alternatives to taxation shroud the actual costs of war, the findings have important implications for democratic accountability and the conduct of conflict.