In the U.S., the Manhattan Project and other projects of the Office of Scientific Research and Development resulted in a much more extensive military-scientific venture, the scale of which dwarfed previous military-funded research projects. Theoretical work by a number of British and American scientists resulted in significant optimism about the possibility of a nuclear chain reaction. As the physicists convinced military leaders of the potential of nuclear weapons, funding for actual development was ratcheted up rapidly. A number of large laboratories were created across the United States for work on different aspects of the bomb, while many existing facilities were reoriented to bomb-related work; some were university-managed while others were government-run, but all were ultimately funded and directed by the military. The May 1945 surrender of Germany, the original intended target for the bomb, did virtually nothing to slow the project's momentum. After Japan's surrender immediately following the atomic bombings of Hiroshima and Nagasaki, many scientists returned to academia or industry, but the Manhattan Project infrastructure was too large—and too effective—to be dismantled wholesale; it became the model for future military-scientific work, in the U.S. and elsewhere.