Many composers emigrated to the United States when the Nazi Party came to power, including Schoenberg, Hindemith, and Erich Korngold . During this period, the Nazi Party embarked on a campaign to rid Germany of so-called degenerate art , which became a catch-all phrase that included music with any link to Jews, Communists, jazz, and anything else thought to be dangerous. Some figures such as Karl Amadeus Hartmann remained defiantly in Germany during the years of Nazi dominance, continually watchful of how their output might be interpreted by the authorities.
The communist German Democratic Republic was established in the historic "Mitteldeutschland" ( Middle Germany ). Former German territories east of the Oder and Neisse rivers, mainly the Prussian provinces of Pomerania , East Prussia , West Prussia , Upper Silesia , Lower Silesia , the eastern Neumark of Brandenburg , and a small piece of Saxony were thus detached from Germany. To compensate Poland for the USSR's annexation of its eastern provinces, the Allies provisionally established Poland's post-war western border at the Oder–Neisse line at the Yalta Conference (1945). As a result, most of Germany's central territories became the Sowjetische Besatzungszone (SBZ, Soviet Occupation Zone). All other lands east of the Oder–Neisse line were put under Polish administration, with the exception of historic northern East Prussia , which went to the USSR.