On October 9, 1941, two months before the United States entered World War II, President Franklin D. Roosevelt approved a crash program to develop an atomic bomb. Ernest Lawrence brought Oppenheimer into the Manhattan Project on October 21. Oppenheimer was assigned to take over the project's specific bomb-design research by Arthur Compton at the Metallurgical Laboratory. On May 18, 1942, National Defense Research Committee Chairman James B. Conant, who had been one of Oppenheimer's lecturers at Harvard, asked Oppenheimer to take over work on fast neutron calculations, a task Oppenheimer threw himself into with full vigor. He was given the title "Coordinator of Rapid Rupture"; "rapid rupture" is a technical term that refers to the propagation of a fast neutron chain reaction in an atomic bomb. One of his first acts was to host a summer school for atomic bomb theory in Berkeley. The mix of European physicists and his own students—a group including Serber, Emil Konopinski, Felix Bloch, Hans Bethe, and Edward Teller—kept themselves busy by calculating what needed to be done, and in what order, to make the bomb.