 In 1940 he moved to Potsdam, and in 1944, with increasingly unacceptable and intolerant demands from the prevailing powers, he left Germany for Switzerland.From 1943 there is a live recording from Berlin of a performance of the Sibelius concerto conducted by Wilhelm Furtwängler with the BPO.From Switzerland he continued to develop his international solo career, and he became successor to Carl Flesch as violin professor at the Lucerne Conservatory.