Pan-European Picnic in the context of Otto von Habsburg

The Warsaw Pact (WP), formally the Treaty of Friendship, Cooperation and Mutual Assistance (TFCMA), was a collective defense treaty signed in Warsaw, Poland, between the Soviet Union and seven other Eastern Bloc socialist republics in Central and Eastern Europe in May 1955, during the Cold War. The term "Warsaw Pact" commonly refers to both the treaty itself and its resultant military alliance, the Warsaw Pact Organisation (WPO) (also known as ‘Warsaw Treaty Organization’ (‘WTO’)). The Warsaw Pact was the military complement to the Council for Mutual Economic Assistance (Comecon), the economic organization for the Eastern Bloc states.

Dominated by the Soviet Union, the Warsaw Pact was established as a balance of power or counterweight to the North Atlantic Treaty Organization (NATO) and the Western Bloc. There was no direct military confrontation between the two organizations; instead, the conflict was fought on an ideological basis and through proxy wars. Both NATO and the Warsaw Pact led to the expansion of military forces and their integration into the respective blocs. The Warsaw Pact's largest military engagement was the Warsaw Pact invasion of Czechoslovakia, one of its own member states, in August 1968. All member states participated except for Albania and Romania, resulting in Albania's withdrawal from the pact less than one month later. The pact began to unravel with the spread of the Revolutions of 1989 through the Eastern Bloc, beginning with the Solidarity movement in Poland, its electoral success in June 1989 and the Pan-European Picnic in August 1989.

The removal of Hungary's border fence with Austria occurred in 1989 during the end of communism in Hungary, which was part of a broad wave of revolutions in various communist countries of Central and Eastern Europe. The border was still closely guarded and the Hungarian security forces tried to hold back refugees. The dismantling of the electric fence along Hungary's 240 kilometres (149 mi) long border with Austria was the first fissure in the "Iron Curtain" that had divided Europe for more than 40 years, since the end of World War II. Then the Pan-European Picnic caused a chain reaction in East Germany that ultimately resulted in the demise of the Berlin Wall.

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.