In early September 1945, he was with the first American team to enter Hiroshima and Nagasaki to assess the damage from the atomic bombs.
While he later became an advocate of arms control, he never became an outspoken critic of nuclear weapons, as did some other Manhattan Project scientists.
Starting as a professor of physics at Columbia in 1951, he became chair of the physics department in 1975, retired from Columbia in 1978, and later was named a professor emeritus at the university.
