Oppenheimer's Plan

In creating the wartime Los Alamos Laboratory, J. Robert Oppenheimer had the sole mission of designing and building an atomic bomb. Accordingly, he organized the laboratory into four technical divisions: Theoretical Physics (T) under Hans Bethe, Experimental Physics (P) under Robert Bacher, Chemistry-Metallurgy (CM) under Joseph Kennedy, and Ordnance Engineering (E) under Navy Captain William Parsons. Each division had a number of groups, with each group having a unique task. Throughout the wartime period, several committees also were used by Oppenheimer to help manage both the administrative and technical work. Among these committees were the Governing Board, which handled many administrative tasks, and the Cowpuncher Committee, which "rode herd" on the development of the implosion (Fat Man) weapon. As the complexities of the technical work increased, so too did the organizational structure.

The Crisis of 1944

In the spring of 1944, experimental data proved that plutonium could not be used in a Little Boy type weapon. In response, Oppenheimer reorganized the entire Laboratory, focusing most of its work on implosion. Without a method of using plutonium, coupled with continuing shortages of uranium, building an atomic bomb might not have been possible during the war.

In this reorganization, T Division remained, as did CM Division. However, both were expanded considerably to help with the increased workload leading up to the Trinity test. E Division was renamed O and given sole responsibility for developing Little Boy. P Division was dissolved. In its place came the Research (R) Division under Robert Wilson, the Gadget Division (G) under Robert Bacher, and (F) Division under Enrico Fermi. Although F Division did not have a formal name, many believe it was named for Fermi. Its primary task was research on the Super, or hydrogen bomb. Of these three new divisions, G Division had the most immediate task – development of the Fat Man bomb. Oppenheimer also created the Explosives (X) Division under Harvard chemist George Kistiakowsky to develop the high explosive lens for Fat Man.

Proof Test

Even with the majority of technical staff working on the implosion device, success did not seem assured. A proof test of the eventual Fat Man device was needed. Consequently, Oppenheimer created Project TR (for Trinity) under Harvard physicist Kenneth Bainbridge to conduct a test of the implosion device. Project TR drew staff from all of the technical divisions. Working under tight security and technical uncertainty, the Trinity Test was successfully conducted in July 1945.

Combat Use

Although success was not certain until Trinity, planning had to be done for combat delivery of the bombs. Physicist Norman Ramsay, on loan to Los Alamos from the War Department, headed this project. Ramsay drew staff primarily from G, X, and O Divisions. It fell to men such as Raemer Schreiber, Philip Morrison, and William Parsons to actually build the bombs on a distant Pacific Island, Tinian, and accompany the devices into combat. Future Los Alamos Director Harold Agnew also was part of this team. The thousands of parts and tools for each weapon were shipped to Tinian, where they were assembled and sent into combat on August 6th and 9th.

Post War Reorganization

The end of World War II brought major organizational changes to Los Alamos. Norris Bradbury succeeded J. Robert Oppenheimer as director in October 1945. Hans Bethe returned to Cornell and was replaced as head of T Division, first by George Plazcek and then Carson Mark. R and F Divisions were combined into a reconstituted P Division under John Manley. When Robert Bacher left the Laboratory, G Division was renamed M Division and placed under Darol Froman. CM became Chemistry, Metallurgy Research (CMR) under Eric Jette. When George Kistiakowsky returned to Harvard, X Division was placed under Max Roy. O Division became Z Division under Gerald Zachariasen and was slowly relocated to Sandia Base where it ultimately became Sandia National Laboratory. Finally, a temporary division, B, was created under Marshall Holloway to handle the Crossroads tests in the summer of 1946.