Sir Joseph (Józef) Rotblat KCMG CBE FRS (4 November 1908 – 31 August 2005) was a Polish physicist, a self-described "Pole with a British passport". Rotblat was the only physicist to leave the Manhattan Project (1942–46) on the grounds of conscience. Rotblat's work on nuclear fallout was a major contribution toward the ratification of the 1963 Partial Nuclear Test Ban Treaty. A signatory of the Russell–Einstein Manifesto (1955), he was secretary-general of the Pugwash Conferences on Science and World Affairs from their founding until 1973. He shared, with the Pugwash Conferences, the 1995 Nobel Peace Prize for efforts toward nuclear disarmament.