In 1942, during World War II, he was called into service at the War Metallurgy Committee in Washington, D.C. In April 1943 he went to work on the Manhattan Project, joining the Chemical-Metallurgical Division at the Los Alamos Laboratory as the head of its Metallurgy Group. When the laboratory was reorganized in April 1944, he became the Associate Division Leader in charge of metallurgy. His first task was recruiting metallurgists, who were in great demand by the war effort. He also had to arrange for the transport of their metallurgical equipment to Los Alamos under wartime conditions.