The decision to use the atom bomb on Japanese cities, and the consequent buildup of enormous nuclear arsenals, was made by governments, on the basis of political and military perceptions.

Józef's early years were spent in what was a prosperous household but circumstances changed at the outbreak of World War I. He was knighted a KCMG in 1998. He was the only physicist to leave the Manhattan Project on the grounds of conscience though others later refused to work on atomic bombs after the defeat of Japan.

Sir Joseph RotblatKCMG CBE FRS (4 November 1908 – 31 August 2005) born Józef Rotblat was a Polish-born British-naturalised physicist. A signatory of the Russell–Einstein Manifesto he was secretary general of the Pugwash Conferences on Science and World Affairs from its founding until 1973. His work on nuclear fallout was a major contribution to the agreement of the Partial Test Ban Treaty.