John Henry Manley (1907-1990) was an American physicist.
Manley worked on the Manhattan Project almost from its beginning, starting at the Metallurgical Lab at the University of Chicago. At the Met Lab, Manley coordinated nationwide fission research and instrument studies for the early Manhattan Project.
In April 1943, Manley was transferred to Los Alamos and became one of Robert Oppenheimer’s chief aides. He managed Los Alamos’ laboratories, surveyed the landscape around the Trinity test site, and witnessed the first nuclear test in July 1945. As one of the principal assistants at Los Alamos, Manley met and worked with many of the Project’s key scientists and figures, including Oppenheimer, Robert Serber, Isidor Rabi, Edward Teller, General Leslie Groves, and Leo Szilard.
At the end of the war, Manley served briefly as the General Secretary of the General Advisory Committee (GAC) of the newly-created Atomic Energy Commission (AEC). He later became an Associate Director of the Los Alamos National Laboratory, serving there from 1946 to 1951. In late 1951, Manley left Los Alamos to become the chairman of physics at the University of Washington in Seattle, but returned six years later as a research adviser. He served at Los Alamos in that capacity until his retirement in 1972.
You can find John Manley’s oral history via the Voices of the Manhattan Project, found here.