The expulsion of Germans led to widespread underpopulation. The population of the town of Glogau fell from 33,500 to 5,000, and from 1939 to 1966 the population of Wrocław fell by 25%. Attempts to repopulate Silesia proved unsuccessful in the 1940s and 1950s, and Silesia's population did not reach pre-war levels until the late 1970s. The Polish settlers who repopulated Silesia were partly from the former Polish Eastern Borderlands, which was annexed by the Soviet Union in 1939. The former German city of Breslau was partly repopulated with refugees from the formerly Polish city of Lwów.