On June 12, 1987, President Ronald Reagan stood just 100 yards away from the concrete barrier dividing East and West Berlin and uttered some of the most unforgettable words of his presidency: “Mr. Gorbachev, tear down this wall.”

By the time Reagan traveled to Berlin, Germany, to commemorate the 750th anniversary of the city’s founding, the Berlin Wall had divided the city in half for nearly 26 years. Built, and officially closed on August 12, 1961, to prevent disaffected East Germans from fleeing the relative deprivations of life in their country for greater freedom and opportunity in the West, the wall was more than just a physical barrier. It also stood as a vivid symbol of the battle between communism and democracy that divided Berlin, Germany and the entire European continent during the Cold War.

The wall’s origins traced back to the years after World War II, when the Soviet Union and its Western allies carved Germany into two zones of influence that would become two separate countries, respectively: the German Democratic Republic (East Germany) and the Federal Republic of Germany (West Germany). Located deep within Soviet-controlled East Germany, the capital city of Berlin was also split in two.

Over the next decade or so, some 2.5 million East Germans—including many skilled workers, intellectuals and professionals—used the capital as the primary route to flee the country, especially after the border between East and West Germany was officially sealed in 1952.

Seeking to stop this mass exodus, the East German government closed off passage between the two Berlins during the night of August 12, 1961. What began as a barbed wire fence, policed by armed guards, was soon fortified with concrete and guard towers, completely encircling West Berlin and separating Berliners on both sides from their families, jobs and the lives they had known before. Over the next 28 years, thousands of people would risk their lives to escape East Germany over the Berlin Wall, and some 140 were killed in the attempt.

Despite its later fame, Reagan’s speech initially received relatively little media coverage, and few accolades, at the time. Western pundits viewed it as misguided idealism on Reagan’s part, while the Soviet news agency Tass called it “openly provocative” and “war-mongering.” And Gorbachev himself told an American audience years later: “[W]e really were not impressed. We knew that Mr. Reagan’s original profession was actor.” (Gorbachev added that Reagan had been “courageously cooperative,” and a great partner and president.)

According to the former Reagan speechwriter Peter Robinson, who drafted the speech, even Reagan’s advisers in the State Department and National Security Council strongly objected, claiming that such a direct challenge would damage the relationship with the new Soviet leader Mikhail Gorbachev. The two nations had been moving closer to peace and even disarmament, especially after a productive summit between Reagan and Gorbachev in Reykjavik in October 1986.

Despite this, the Berlin Wall—that heavily fortified symbol of Cold War divisions—seemed as solid as ever.

On June 12, 1987, standing on the West German side of the Berlin Wall, with the iconic Brandenburg Gate at his back, Reagan declared: “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.” Reagan then waited for the applause to die down before continuing. “Mr. Gorbachev, tear down this wall!”

Reagan’s tactics were a departure from his three immediate predecessors, Presidents Richard Nixon, Gerald Ford and Jimmy Carter, who all focused on a policy of détente with the Soviet Union, playing down Cold War tensions and trying to foster a peaceful coexistence between the two nations. Reagan dismissed détente as a “one-way street that the Soviet Union has used to pursue its own aims.”

On November 9, 1989, the Cold War officially began to thaw when Egon Krenz, the head of East Germany’s Communist Party, announced that citizens could now cross into West Germany freely. That night, thousands of East and West Germans headed to the Berlin Wall to celebrate, many armed with hammers, chisels and other tools. Over the next few weeks, the wall would be nearly completely dismantled. After talks over the next year, East and West Germany officially reunited on October 3, 1990.

This was a result of many changes over the course of two years. Gorbachev’s reforms within the Soviet Union gave Eastern Bloc nations more freedom to determine their own government and access to the West. Protests within East Germany gained strength, and after Hungary and Czechoslovakia opened their borders, East Germans began defecting en masse.

The “Tear Down This Wall” speech didn’t mark the end of Reagan’s attempts to work with Gorbachev on improving relations between the two rival nations: He would join the Soviet leader in a series of summit meetings through the end of his presidency in early 1989, even signing a major arms control agreement, the Intermediate-Range Nuclear Forces (INF) Treaty.

In the aftermath of the Berlin Wall’s fall, many began to reevaluate Reagan’s earlier speech, viewing it as a harbinger of the changes that were then taking place in Eastern Europe. In the United States, Reagan’s challenge to Gorbachev has been celebrated as a triumphant moment in his foreign policy, and as Time magazine later put it, “the four most famous words of Ronald Reagan’s presidency.”

In the end, Gorbachev’s reforms, and the resulting protest movements put pressure on the East German government to open barriers to the West.  Gorbachev was awarded the Nobel Peace Prize in 1990 for his work in ending the Cold War, including the fall of the Berlin Wall.

While Gorbachev's role in thawing the Cold War was clear, Reagan's words became memorable. As Douglas Brinkley, professor of history at Rice University, told CBS News in 2012, Reagan’s speech is “seen as a turning point in the Cold War” because it “bolstered the morale of the pro-democracy movement in East Germany.” Yet the greatest impact of the speech may have been the role it played in the creation of Reagan’s enduring legacy as president, and in solidifying his legendary status among his supporters as the “great communicator.”