Rosbaud was in Oslo from August 26 to September 16, 1939, a few days before Frank Foley abandoned Berlin and transferred to Oslo. There he visited Victor Goldschmidt, a geologist who studied the properties of uranium and "super-uranium" (plutonium). In Oslo Rosbaud also met Odd Hassel, an old acquaintance. Goldschmidt and Rosbaud were friends and when the persecution of Jews in Germany intensified in 1935, Rosbaud helped Goldschmidt abandon Göttingen and return to Oslo. In late autumn 1939 Rosbaud again visited Oslo and urged Odd Hassel to warn Norwegian authorities about a likely German invasion of Norway.