After the invasion of Poland by Nazi Germany and the Soviet Union in 1939, Lwów initially came under Soviet occupation. During this period Weigl's institute continued to function, although Poles, particularly those escaping from the German-controlled areas, were banned from being employed there. The Soviet authorities deported ethnic Poles from the seized territories, sending them to Kazakhstan, Siberia and other areas deep within the Soviet Union. Nevertheless, despite the official prohibition on employment, Weigl used his prestige and influence (during this time Nikita Khrushchev visited the institute) to secure the release of several Polish would-be deportees and in some cases managed to obtain permission for those who had already been exiled to return. These individuals were then given work in the institute as either nurses, interpreters (Weigl himself did not speak Russian) or as some of the first lice feeders; people who were given the job as a means of protecting them from persecution by the Soviet authorities.