Germany's unification in October 1990 was one of the most momentous events in European history in the second half of the twentieth century. Its unique historical value stems from the highly symbolic and emotional significance of the events that made the unification of the two German states possible. German unity ended the Cold War in Europe, which for forty years had divided Germany and the continent. It knocked down the remaining vestiges of the bipolar order that had emerged at the end of World War II and drew back the Iron Curtain, accelerating the process leading to the collapse of communist regimes across Eastern Europe and to the disintegration of the Union of Soviet Socialist Republics (USSR) in December 1991. At the same time, it marked the demise of the logic of limited sovereignty and the rise of self-determination and liberal democracy in the former Soviet bloc, ushering in a dramatic acceleration in the process of Europe's political and economic integration and triggering the beginning of NATO's post-Cold War transformation and enlargement.

This revolutionary process occurred first and foremost as a consequence of widespread political and social discontent across the Soviet bloc. The East German people's action against their own rulers also played a dramatic role. It began in May 1989 when, inspired by the new Soviet leadership's reforms and by the growth of democratic movements in neighbouring Poland, Hungary and Czechoslovakia, a truly peaceful popular revolt undermined and overwhelmed the dictatorial regime, which had ruled Eastern Germany since the late 1940s with ironclad support from Moscow.