An open world
Early on during his exile, Bohr became convinced that the existence of the bomb would not only seem to necessitate but should also, due to the urgency of mutual confidence, facilitate a new approach to the problems of international relationship. The first step toward avoiding a postwar nuclear arms race would be to inform the ally in the war, the Soviet Union, of the project. Bohr set out on a solitary campaign, during which he even succeeded in obtaining personal interviews with British Prime Minister Winston Churchill and U.S. President Franklin D. Roosevelt. He was unable to convince either of them of his viewpoint, however, instead being suspected by Churchill of spying for the Russians. After the war, Bohr persisted in his mission for what he called an open world between nations, continuing his confidential contact with statesmen and writing an open letter to the United Nations in 1950.
Bohr was allowed to return home only after the atomic bomb had been dropped on Japan in August 1945. In Denmark he was greeted as a hero, some newspapers even welcoming him with pride as the Dane who had invented the atomic bomb. He continued to run and expand his institute, and he was central in postwar institution building for physics. On a national scale, he took a major part in establishing the research facility at Risø, near Roskilde, only a few miles outside Copenhagen, created in order to prepare the introduction of nuclear power in Denmark, which, however, has never occurred. Internationally, he took part in the establishment of CERN, the European experimental particle physics facility near Geneva, Switz., as well as of the Nordic Institute for Atomic Physics (Nordita) adjacent to his institute. Bohr left behind an unsurpassed scientific legacy, as well as an institute that remains one of the leading centres for theoretical physics in the world.