And they knew they could trust each other. Stasi interrogators had once asked a prisoner named Katrin Hattenhauer, a young rebel, how she and her fellow dissidents held together despite all of the Stasi’s actions against them. She replied that shared suffering welded people together more strongly than shared success: “Where the hammer has come down, whatever is underneath is going to hold together.”

In contrast, Stasi files demonstrate how members of the regime did not trust their colleagues, or their subordinates — and that this lack of trust gravely undermined their ability to blunt the rising revolution. And so, when tens of thousands of Berliners headed toward the wall in the minutes after the news conference, the entire system cracked.

When one of the regime’s most loyal subordinates, a Stasi officer named Harald Jäger who was working the Nov. 9 night shift at a crucial checkpoint in the Berlin Wall, repeatedly phoned his superiors with accurate reports of swelling crowds, they did not trust or believe him. They called him a delusional coward. Insulted, furious and frightened, he decided to let the crowds out, starting a chain reaction that swept across all of the checkpoints that night.

In short, the fall of the wall came about because of the complex interplay among Soviet reforms, East Berlin’s incompetence and, crucially, rising opposition from everyday Germans. As another dissident, Marianne Birthler, puts it, Westerners believe that “it was the opening of the wall that brought us our freedom.” Rather, “it was the other way around. First we fought for our freedom; and then, because of that, the wall fell.”

This doesn’t mean the West was irrelevant. The attractiveness of the freedoms of the West, both political and commercial, served as motivation for large numbers of East Germans, as shown clearly by their later vote for rapid German reunification on Western terms. And the support that the United States gave both to its allies in Western Europe and to dissidents in Eastern Europe over the course of the long Cold War helped to shape an environment in which the wall could open.

But that support did not open the barrier all by itself. Rather than congratulate itself for things that it did not do, on this anniversary Washington should learn from what it did do. Playing a long game, it helped to create a context in which locals could seize on opportunities to overcome their own dictators. That is indeed a success worth celebrating.