When do U.S. presidents change policy to respond with increased intensity to mass killings of civilians in other countries? The twentieth century witnessed a series of state-sponsored mass killings in a variety of regions around the world. Conventional arguments suggest that although the United States has the capability of responding to such atrocities, it often fails to do so because of a lack of political will for action. Historical evidence suggests, however, that although the modal response of the United States is inaction, at times U.S. presidents reverse course to respond more forcefully to mass killings. Three factors explain when and why these policy shifts happen: the level at which dissent occurs within the U.S. government, the degree of congressional pressure for policy change, and the extent to which the case of mass killing poses a political liability for the president. President Franklin D. Roosevelt's creation of the War Refugee Board in 1944 during the Holocaust supports this theory.