Houtermans was a Communist; he had been a member of the German Communist Party since the 1920s. After Adolf Hitler came to power in 1933, Charlotte Houtermans insisted that they leave Germany. They went to Great Britain, near Cambridge, where he worked for the EMI (Electrical and Musical Instruments, Ltd.) Television Laboratory. In 1935 Houtermans emigrated to the Soviet Union, as the result of a proposal by Alexander Weissberg, who had emigrated to there in 1931. Houtermans took an appointment at the Kharkov Physico-Technical Institute and worked there for two years with the Russian physicist Valentin P. Fomin. In the Great Purge, Houtermans was arrested by the NKVD in December 1937. He was tortured and confessed to being a Trotskyist plotter and German spy, out of fear from threats against Charlotte. However, Charlotte had already escaped from the Soviet Union to Denmark, after which she went to England and finally the USA. After the Hitler-Stalin Pact of 1939, Houtermans was turned over to the Gestapo in May 1940 and imprisoned in Berlin. Through efforts of Max von Laue, Houtermans was released in August 1940, whereupon he took a position at "Forschungslaboratorium für Elektronenphysik", a private laboratory of Manfred Baron von Ardenne, in Lichterfelde, a suburb of Berlin. In 1944, Houtermans took a position as a nuclear physicist at the Physikalisch-Technische Reichsanstalt.