Bethe and Fermi riding in jeep on the Los Alamos grounds during the Manhattan Project. Hans Albrecht Bethe (July 2, 1906 - March 6, 2005) was a German-American nuclear physicist, and Nobel laureate in physics for his work on the theory of stellar nucleosynthesis, 1967. He also made important contributions to quantum electrodynamics, nuclear physics, solid-state physics and astrophysics. During World War II, he was head of the Theoretical Division at the Los Alamos laboratory which developed the first atomic bombs where he played a key role in calculating the critical mass of the weapons, and did theoretical work on the implosion method used in both the Trinity test and the "Fat Man" weapon dropped on Nagasaki, Japan. Enrico Fermi (1901-1954) was an an Italian-born, naturalized American physicist particularly known for his work on the development of the first nuclear reactor, Chicago Pile-1, and for his contributions to the development of quantum theory, nuclear and particle physics, and statistical mechanics. He was awarded the 1938 Nobel Prize in Physics for his work on induced radioactivity.