West & East reunification

The war resulted in the death of nearly ten million German soldiers and civilians; large territorial losses; the expulsion of about 15 million Germans from its former eastern territories and other countries; and the destruction of multiple major cities. The national territory and Berlin were partitioned by the Allies into four military occupation zones. The sectors controlled by France, the UK, and the USA were merged on 23 May 1949, to form the Federal Republic of Germany; on 7 October 1949, the Soviet Zone established the German Democratic Republic. They were informally known as "West Germany" and "East Germany" and the two parts of Berlin as "West Berlin" and "East Berlin". The eastern and western countries opted for East Berlin and Bonn as their respective capitals. However, West Germany declared the status of its capital Bonn as provisional,in order to emphasize its stance that the two-state solution was an artificial status quo that was to be overcome one day.
West Germany : established as a liberal parliamentary republic with a "social market economy" , was allied with the United States, the UK and France. The country eventually came to enjoy prolonged economic growth beginning in the early 1950s (Wirtschaftswunder). West Germany joined NATO in 1955 and was a founding member of the European Economic Community in 1958. Across the border, East Germany was at first occupied by, and later (May 1955) allied with, the USSR. An authoritarian country with a Soviet-style command economy, but many of its citizens looked to the West for political freedoms and economic prosperity. The Berlin Wall, built in 1961 to stop East Germans from escaping to West Germany, became a symbol of the Cold War. However, tensions between East and West Germany were somewhat reduced in the early 1970s by Chancellor Willy Brandt's Ostpolitik, which included the de facto acceptance of Germany's territorial losses in World War II.
In the face of a growing migration of East Germans to West Germany via Hungary and mass demonstrations during the summer of 1989, East German authorities unexpectedly eased the border restrictions in November, allowing East German citizens to travel to the West. Originally intended as a pressure valve to retain East Germany as a state, the opening of the border actually led to an acceleration of the reform process in East Germany, which finally concluded with the Two Plus Four Treaty a year later on 12 September 1990 and German reunification on 3 October 1990. Under the terms of the treaty, the four occupying powers renounced their rights under the Instrument of Surrender, and Germany regained full sovereignty. Based on the Bonn-Berlin-Act, adopted by the parliament on 10 March 2004, the capital of the unified state was chosen to be Berlin, while Bonn obtained the unique status of a Bundesstadt (federal city) retaining some federal ministries.
Since reunification, Germany has taken a leading role in the European Union and NATO. Germany sent a peacekeeping force to secure stability in the Balkans and sent a force of German troops to Afghanistan as part of a NATO effort to provide security in that country after the ousting of the Taliban. These deployments were controversial, since after the war, Germany was bound by law to only deploy troops for defence roles. Deployments to foreign territories were understood not to be covered by the defence provision; however, the parliamentary vote on the issue effectively legalised the participation in a peacekeeping context.