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. 
Egon Krenz was elected by the politburo to be Honecker's successor. Krenz tried to show that he was looking for change within the GDR but the citizens did not trust him. On November 9, 1989, the SED announced that East Germans would be able to travel to West Berlin the next day. The spokesman who announced the new travel law incorrectly said that it would take effect immediately, implying the Berlin Wall would open that night. People began to gather at border checkpoints at the wall hoping to be let through, but the guards told them that they had no orders to let citizens through. As the number of people grew, the guards became alarmed and tried to contact their superiors but had no responses. Unwilling to use force, the chief guard at the checkpoint relented at 10:54pm and ordered the gate to be opened. Thousands of East-Germans swarmed into West Berlin and the purpose of the wall was deemed now obsolete. The fall of the wall destroyed the SED politically as well as the career of its leader, Egon Krenz. On December 1, 1989, the GDR government revoked the law that guaranteed the SED the right to rule the East German political system, effectively ending communist rule in the GDR.