Joseph Rotblat - Manhattan Project

Manhattan Project

While still in Poland, Rotblat had realised that his work could be used to produce a bomb. He first thought that he should "put the whole thing out of my mind", but with the rise of Nazi Germany he continued because he thought the only way to prevent Nazi Germany from using a nuclear bomb was if Britain had one to act as a deterrent. After the start of the war, he started working explicitly with Chadwick on bomb work.

Early in 1944 Rotblat went with James Chadwick's group to work on the Manhattan Project to build the first atomic bombs. The usual condition for people to work on the Manhattan Project was that they had to become U.S. citizens or British subjects. Rotblat declined and the condition was waived. He continued to have strong reservations about the use of science to develop such a devastating weapon and was shocked in March 1944, at a private dinner at the Chadwick's, to hear Leslie Groves say "Of course, the real purpose in making the bomb was to subdue the Soviets". By the end of 1944 it was also apparent that Germany had abandoned the development of its own bomb and Rotblat asked to leave the project. Chadwick was then shown a security dossier in which Rotblat was accused of being a Soviet spy and that, having learnt to fly at Los Alamos, he was suspected of wanting to join the Royal Air Force so that he could fly to Poland and defect to the Soviet Union. In addition, he was accused of visiting someone in Santa Fe and leaving them a blank cheque to finance the formation of a communist cell.

In fact, Rotblat was able to show that much of the information within the dossier had been fabricated. In addition, FBI records show that in 1950, Rotblat's friend in Santa Fe was tracked down in California, and she flatly denied the story: in fact, the cheque had never been cashed and had been left to pay for items not available in the U.K. during the war. In reminiscences from 1985 Rotblat tells how a box containing "all my documents" went missing on a train ride from Washington D.C. to New York as he was leaving the country, but the presence of large numbers of Rotblat's personal papers from Los Alamos now archived at the Churchill Archives Centre "is totally at odds with Rotblat's account of events". Rotblat was not permitted to re-enter the United States until 1964. Rotblat 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.