Harold Urey
During World War II, Urey's team at Columbia worked on a number of research programs that contributed towards the Manhattan Project to develop an atomic bomb for the United States. Most importantly, they developed the gaseous diffusion method to separate uranium-235 from uranium-238. In autumn 1941, Urey, with G.B. Pegram, led a diplomatic mission to England to establish co-operation on the development of the atomic bomb.