Niels Bohr fled to Sweden in 1943 to escape the Nazis. When German authorities moved against Denmark’s Jewish population, Bohr learned that his own arrest was likely because of his Jewish ancestry and scientific prominence. He escaped from occupied Denmark with his family and reached Sweden aboard a fishing boat.
Sweden was officially neutral during World War II, making it a crucial refuge for Danish civilians. From there, Bohr continued to London and eventually traveled to the United States, where he contributed to Allied atomic research. His escape was part of the wider rescue of Danish Jews in October 1943, when many were transported across the Øresund to safety in Sweden.
A common mix-up is answering “the United States,” since Bohr later worked with the Manhattan Project there. However, Sweden was the country he first fled to from Nazi-occupied Denmark. His son Aage escaped with him and later became a Nobel Prize-winning physicist.