Why did Niels Bohr escape from Denmark in 1943?

Niels Bohr escaped from Denmark in the fall of 1943 primarily because the political situation in the country had deteriorated following the collapse of the Danish government’s collaboration with the German occupiers.1

After receiving a warning that his arrest was imminent, Bohr fled by boat with his family across the sound to Sweden. While he had previously declined an invitation from James Chadwick to join the Allied atomic bomb project in England—believing at the time that such a weapon was not feasible during the war—his perspective changed upon arriving in London. Once briefed on the progress of the Allied effort, he became concerned about the potential for a German nuclear project and subsequently joined the Manhattan Project to contribute his expertise.1