This is an analysis of US economic policy and security post-war planning in the Departments of State and Treasury during World War II. The planning commenced early in the war and culminated in the conferences of Bretton Woods and Dumbarton Oaks in the summer and autumn of 1944. While both departments advocated similar goals of ensuring international economic prosperity and military security after the war, they followed different strategies to achieve these goals. The Treasury Department insisted that only states that would adhere to strict fiscal and trade rules designed to increase the volume of international commerce could join the new International Monetary Department. The State Department, in contrast, did not impose such prerequisites to any state joining the collective security structure. The book offers an explanation why the two departments differed in their approach to post-war planning.