 Oppenheimer was not reappointed to the GAC when his term expired in 1952, and Rabi succeeded him as chairman, serving until 1956. Rabi later testified on Oppenheimer's behalf at the Atomic Energy Commission's controversial security hearing in 1954 that led to Oppenheimer being stripped of his security clearance. Many witnesses supported Oppenheimer, but none more forcefully than Rabi:
