 Late in 1940, he returned to the Treasury Department as an assistant director of monetary research, where he stayed for about a year, during which he was special assistant to the United States Ambassador in England.In 1942, he became Executive Secretary of the Joint War Production Committee of the United States and Canada and an assistant to the Executive Director of the Board of Economic Warfare (later renamed the Foreign Economic Administration).In late 1944/early 1945, Coe was named Director of the Division of Monetary Research in the Treasury Department, serving as technical secretary at the United Nations Monetary and Financial Conference at Bretton Woods, New Hampshire in 1944, he accepted a position as Secretary of the International Monetary Fund in 1946, his successor at Treasury being Harold Glasser.