Enlarge image US President Ronald Reagan visited Berlin on its 750th anniversary in 1987, where he delivered a rousing speech. He is flanked by German Chancellor Helmut Kohl (r) and West Berlin Mayor Eberhard Diepgen (l). (© picture-alliance/dpa) On June 12, 1987, US President Ronald Reagan stood before the Brandenburg Gate at the heart of Berlin and delivered a challenge to the Soviet leader at the time. "Mr. Gorbachev, open this gate. Mr. Gorbachev, Mr. Gorbachev, tear down this wall!"

That speech - heard round the world on that day 25 years ago - has gone down in history as a call for freedom and democracy.

Reagan speech was an appeal for freedom

President Reagan and First Lady Nancy Reagan arrived from a G-7 summit in Italy for a brief visit to Berlin on June 12, 1987. They were taken to the Reichstag, where they viewed the Berlin Wall from a balcony. (The Reichstag is Germany's historic parliament building, and today once again serves as the seat of the Bundestag, or German Parliament.)

Their visit, which coincided with Berlin's 750th anniversary, came during a time of heightened East-West tensions, caused in particular by debate over the stationing of short-range American missiles in Europe to protect the Western European NATO alliance countries - including the former West Germany - from potential Soviet aggression. President Reagan believed that Western democracy - and the promotion of more free speech in the former Soviet Union and Eastern bloc countries - offered the best hope to open up the Berlin Wall.

Enlarge image The Brandenburg Gate at the heart of the city behind the Berlin Wall. (© picture-alliance/dpa)

Berlin's iconic Brandenburg Gate - which was located at the time behind the Berlin Wall, in East Berlin - was chosen as the ideal symbolic site for President Reagan's speech. He was strategically positioned close to the Berlin Wall before two massive panels of bulletproof glass to protect him from potential snipers in East Berlin. Some 45,000 people were reportedly in attendance, along with German Chancellor Helmut Kohl, German President Richard von Weizsäcker, and West Berlin Mayor Eberhard Diepgen.

• "We welcome change and openness; for we believe that freedom and security go together, that the advance of human liberty can only strengthen the cause of world peace. There is one sign the Soviets can make that would be unmistakable, that would advance dramatically the cause of freedom and peace. General Secretary Gorbachev, if you seek peace, if you seek prosperity for the Soviet Union and eastern Europe, if you seek liberalization, come here to this gate. Mr. Gorbachev, open this gate. Mr. Gorbachev, Mr. Gorbachev, tear down this wall!" - President Reagan, June 12, 1987

Enlarge image "The wall will fall. Beliefs become reality." - A memorial to the victims of the Berlin Wall photographed in West Berlin on October 10, 1986. (© Lyricmac/Wikimedia Commons)

Chancellor Kohl has said that he would never forget Reagan's challenge to Gorbachev to tear down the Berlin Wall. "He was a stroke of luck for the world, especially for Europe," Kohl has been quoted as saying.

Although some differing views have been expressed over just how much influence Reagan's words may have had on the subsequent 1989 fall of the Berlin Wall, the speech has been widely chronicled as an important moment in Cold War history.

Later in his speech, President Reagan (1911-2004) also spoke these words:

• "As I looked out a moment ago from the Reichstag, that embodiment of German unity, I noticed words crudely spray-painted upon the wall, perhaps by a young Berliner, 'This wall will fall. Beliefs become reality.' Yes, across Europe, this wall will fall. For it cannot withstand faith; it cannot withstand truth. The wall cannot withstand freedom."

Fall of the Berlin Wall followed in 1989

Enlarge image Thousands of revelers clambered up the Berlin Wall to celebrate its demise in November 1989. (© picture-alliance/dpa)

Although it may seem hard to believe now, no one could have imagined at the time that just two years later, on November 9, 1989, the Berlin Wall that had artificially divided the city for nearly three decades would be peacefully opened by the former communist East Germany, which could no longer resist mounting pressure from an increasingly active East German population engaged in political protests aimed at promoting freedom and democracy. This allowed East Berliners to freely cross over into West Berlin for the first time since the wall was constructed in 1961.

Beginning of the end of the Cold War era

This was a historic turning point that marked the beginning of the end of the Cold War era and took the entire world by surprise. Where watchtowers manned by guards with shoot-to-kill orders if anyone dared to flee from East to West Berlin had stood for decades, people could suddenly freely make this short journey on foot.

One of the most jubilant moments in human history

Enlarge image East Berliners drive their traditional Trabant, or "Trabi," cars through Checkpoint Charlie and are greeted by cheering West Berliners. (© picture-alliance/dpa)

They were greeted on the other side by jubilant crowds in what quickly morphed into a massive multi-day party at the center of Germany's biggest city. Images of people dancing on the Berlin Wall, of stunned uniformed East German soldiers sharing a laugh with their fellow German citizens (from both "East" and "West" Berlin) and of East Germans driving through formerly blocked and heavily guarded checkpoints into West Berlin in their tiny Trabant ("Trabi") cars went round the world - just like Reagan's speech held right before the Berlin Wall at the Brandenburg Gate just two years earlier.

The Day of German Unity

Germany, which had been artificially divided after the Second World War into two separate political entities - the former democratic West Germany and the former communist East Germany - was finally reunified on October 3, 1990, which has been celebrated as a national holiday known as "The Day of German Unity" ever since.