German reunification (German: Deutsche Wiedervereinigung), also known as the expansion of the Federal Republic of Germany (BRD), was the process of re-establishing Germany as a single sovereign state, which began on 9 November 1989 and culminated on 3 October 1990 with the dissolution of the German Democratic Republic and the integration of its re-established constituent federated states into the Federal Republic of Germany to form present-day Germany. This date was chosen as the customary German Unity Day, and has thereafter been celebrated each year as a national holiday. On the same date, East and West Berlin were also reunified into a single city, which eventually became the capital of Germany.
The East German government, controlled by the Socialist Unity Party of Germany (SED), started to falter on 2 May 1989, when the removal of Hungary's border fence with Austria opened a hole in the Iron Curtain. The border was still closely guarded, but the Pan-European Picnic and the indecisive reaction of the rulers of the Eastern Bloc started off an irreversible movement. It allowed an exodus of thousands of East Germans fleeing to West Germany via Hungary. The Peaceful Revolution, part of the international revolutions of 1989 including a series of protests by East German citizens, led to the fall of the Berlin Wall on 9 November 1989 and the GDR's first free elections on 18 March 1990, and then to negotiations between the two countries that culminated in a Unification Treaty. Other negotiations between the two Germanies and the four occupying powers in Germany produced the Treaty on the Final Settlement with Respect to Germany, which granted on 15 March 1991 full sovereignty to a reunified German state, whose two parts had previously been bound by a number of limitations stemming from their post-World War II status as occupation zones, though it was not until 31 August 1994 that the last Russian occupation troops left Germany.
