After being arrested, along with two of his sons, on the night of the German invasion of Austria, March 11, 1938, Loewi was released after three months on condition that he "voluntarily" relinquish all his possessions, including his research, to the Nazis. He went initially to Britain and shortly afterwards the he was offered a visiting professorship at the Université libre de Bruxelles via the Francqui Foundation. Loewi moved to the United States in 1940, where he became a research professor at the New York University College of Medicine. In 1946, he became a naturalized citizen of the United States. In 1954, he became a Foreign Member of the Royal Society. He died in New York City on December 25, 1961.