This article is part of our series of explainers on key moments in the past 100 years of world political history. In it, our authors examine how and why an event unfolded, its impact at the time, and its relevance to politics today.

Nearly 30 years ago, in the night of November 9-10, 1989, East German border police opened the gates at crossing points in the Berlin Wall, allowing masses of East Berliners to stream through them unhindered.

This started a night of unbridled celebrations as people crossed freely back and forth through the Cold War barrier, climbed on it, and even danced and partied on it.

The signal for the mass breach of the previously heavily guarded wall was a fumbled announcement in a press conference by the Socialist Unity Party (SED) Party chief of Berlin, Günter Schabowski.

His announcement that travel restrictions for East German citizens would be lifted led to the Wall’s transit points being mobbed by thousands of East Germans as they interpreted the announcement to mean immediate freedom of movement to the West.

West German citizens gather at opening in the Berlin Wall, November 1989.

What happened?

The opening of the Berlin Wall triggered a series of events that led to an unexpectedly rapid unification of the Federal Republic of Germany (FRG or West Germany) and the German Democratic Republic (GDR, or East Germany) on October 3, 1990.

But to really understand this moment, we need to look at when and why the Berlin Wall was erected in the first place. Following Germany’s defeat in the second world war, the country was split between the victors – the Western Allies’ occupation zones became the Federal Republic in 1949, while the Soviet zone was reconstituted as the German Democratic Republic shortly thereafter.

Germany’s capital, Berlin, was also split down the middle. The wall was erected by the East German leadership in August 1961 to stop the flow of citizens from East to West, completing a sealed border that elsewhere ran along the frontier between the two German states.

The Wall’s opening was the product of two processes that had gathered momentum throughout the second half of 1989: the peaceful demonstrations and protest marches of a number of newly constituted East German civil rights organisations, and the growing number of East German citizens leaving from the GDR’s side doors.

The latter mostly happened through Hungary, which opened its border with Austria in May. Large numbers of East Germans on holidays in Hungary took advantage of the opportunity to migrate to West Germany. By November 1989, the trickle of East Germans leaving had become a flood, with thousands a day going to the West by the week the wall was opened.

Furthermore, the East German SED leadership had been increasingly on the back foot since peaceful demonstrations started, following manipulated local government elections in May 1989.

East German students sitting on the Berlin Wall in front of border guards.

By the start of October, there were regular Monday night protest marches through Leipzig and other East German cities. Initially, there were fears that the SED leadership might suppress these protests with violence.

The Tiananmen Square protests and subsequent mass killings in Beijing in June 1989 were fresh in the minds of many….