Bohr, Oppenheimer, Einstein.

During WWII Bohr tried to convince Roosevelt and Churchill to work together with the Soviets in the Manhattan project to speed up the results. He tried to argue that it was extremely dangerous to have separate development of nuclear weapons by several powers rather than some form of controlled sharing of the knowledge. Churchill would not hear of it. In 1944 the allies learned that germans had no atomic weapons and Bohr hoped then that greater atomic armament could be prevented by new international agreements, before the weapons could be used in war. He also hoped that new contacts could be established between Western and Russian nuclear scientists, as signs of cooperation between the soon-to-be victorious powers in the war. Both Roosevelt and Churchill did not think so. In June 1950 he addressed an "Open Letter" to the United Nations calling for international cooperation on nuclear energy.

Oppenheimer is often called the ‘father of the atomic bomb’. After the war he was chief advisor to the Atomic Energy Commission and used that position to lobby for international control of nuclear power to avert nuclear proliferation and an arms race with the Soviet Union. After provoking the ire of many politicians with his outspoken opinions he had his security clearance revoked in a much-publicised hearing in 1954, and was effectively stripped of his direct political influence; In a TV broadcast in 1965, he said this about the Trinity nuclear test, the first ever nuclear test in New Mexico: “We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita; Vishnu is trying to persuade the Prince that he should do his duty and, to impress him, takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another.”

Einstein was a known pacifist. He hated armies. Yet he supported the Manhattan project. In a letter he sent to Roosevelt he wrote that there is the possibility that German scientists might win the race to build an atomic bomb, and warned him that Hitler would be more than willing to resort to such a weapon. He recommended that the US become directly involved in Uranium research – this led to the Manhattan project. In a letter to a friend one year before he died he wrote: "I made one great mistake in my life — when I signed the letter to President Roosevelt recommending that atom bombs be made; but there was some justification — the danger that the Germans would make them”. In 1945 he realised that an atomic arms race might begin and wrote another letter to Roosevelt enclosing a warning against using the A-bomb. The letter was still unopened on Roosevelt's desk when he died. Einstein was chairman of the Emergency Committee of Atomic Scientists, set up in 1946; its aims were to educate the public about the dangers of atomic warfare, to promote the benign use of atomic energy, and to work for the abolition of war. Not afraid of swimming against the tide, he tried hard to create links with the Soviet Union and to prevent the escalation of the Cold War.