The Danish physicist Niels Bohr, whose mother was Jewish, made a determined stand for his fellow countrymen in a personal appeal to the Swedish king and government ministers. King Gustav V granted him an audience after a persuasive call from Greta Garbo, who knew Bohr. He was spirited off to Sweden, whose government arranged immediate transport for him to the United States to work on the then top-secret Manhattan Project. When Bohr arrived on Swedish soil, government representatives told him he had to board an aircraft immediately for the United States. Bohr refused. He told the officials—and eventually the king—that until Sweden announced over its airwaves and through its press that its borders would be open to receive the Danish Jews, he was not going anywhere. Bohr wrote of these events himself. As related by the historian Richard Rhodes, on September 30 Bohr persuaded King Gustaf V of Sweden to make public Sweden's willingness to provide asylum, and on October 2 Swedish radio broadcast that Sweden was ready to receive the Jewish refugees. Historian Richard Rhodes and others interpret Bohr's actions in Sweden as being a necessary precursor without which mass rescue could not have occurred. According to Paul A. Levine, however—who does not mention the Bohr factor at all—the Swedish Ministry for Foreign Affairs acted on clear instructions given much earlier by Prime Minister Per Albin Hansson and Foreign Minister Christian Günther, following a policy already established in 1942.