We thought it meant the end of international contention. We thought it meant the nuclear menace was no more. We thought it meant Russia and America, the two powers of the future envisioned by de Tocqueville, could be friends. We thought it meant the end of espionage. We thought it might even be the end of history.

We were wrong, dead wrong, tragically wrong, about all of it, because we did what great powers always do when they are engaged in great contests. We thought that if only we could get through the Cold War (or World War I, or World War II) we would enter the sunlit uplands, where serenity and prosperity reigned, purchased effortlessly by (and this was the phrase that was brandished in the capital and from coast to coast two decades ago) the peace dividend. To paraphrase Churchill: Some peace. Some dividend.

The realists and pragmatists would deny us these reveries, but great struggles require great hopes and they almost always inspire great myths, and if you do not believe me, consider how bright a world was forecast by the abolitionists during the Civil War or by Woodrow Wilson during the Great War, whose sad centenary we are only five years from commemorating. The peace is never as bright as the one we yearn for in the darkness of the storm.

All of this brings us to the fall of the Berlin Wall, which began 20 years ago tomorrow, and to an unrecognized truth:

Even though things have not turned out as we hoped they might in November 1989 — the eagle has not laid down beside the bear, for example — this is still a world far preferable to the one we occupied at various points in the 20th century, when angry nations seethed at each other across militarized borders separating South and North Korea, and Vietnam, or across the Oder-Neisse Line, the Curzon Line and multiple other lines in Europe’s sand.

Today we face frightful challenges, some involving the economy (the recovery of 2009 still seems elusive) and some involving national security (global terrorism adds a new form of instability to world affairs), but we ought to remember 1989 as one of the great divides in modern history.

It effectively brought to an end a world struggle, beginning with the Russian Revolution in 1917, between two competing economic systems and ideologies whose adherents believed were irreconcilable. This struggle was the leitmotif of almost all of 20th-century history, even if it was repressed between 1941 and 1945, when for reasons that were nothing more than opportunistic, the two systems united to fight a third system so odious that the world had not seen its like before or since.

Indeed, from our vantage point in 2009, it is possible to say that all of history between 1917 and 1989 — the short 20th century, you might say — was preoccupied with this struggle.

It was a large motivation behind Woodrow Wilson’s Fourteen Points; he wanted to offer the world a utopian vision that could compete with Lenin’s. It was an important subtext in World War II; Churchill warned of an ascendant Soviet Union even as Franklin D. Roosevelt was cozying up to Stalin at Tehran and Yalta. And it dominated the life of nations big (the two Germanys) and small (Cuba, Vietnam, Laos, Cambodia, Korea, Angola, Nicaragua, Grenada) for a half century after World War II.

We still have much to learn from the Cold War. Did we learn the lessons of Munich and appeasement well, or too well? Did our dedication to winning the Cold War allow us almost to lose the best part of the civil rights movement, many of whose leaders were pilloried for being Moscow sympathizers? Did our zeal to protect freedom in a world where our rivals wished to destroy freedom help to erode our own freedoms? (This last is a question we still might ask.)

In those decades after Bernard Baruch first used the expression “Cold War” — in a speech written by Herbert Bayard Swope — tens of millions of people lived in danger or in fear. A younger generation may giggle smugly at the Civil Defense videos (all that diving under flimsy school desks), the crumbling and rotting supplies of government-issued biscuits (some of them no doubt still in the basement of post offices and courthouses) and the moral questions of the time (what to do when your neighbor bangs at the door of your fallout shelter?).

But in those days Americans had more to fear than fear itself.

The Cold War contaminated the nation’s politics, transforming a two-bit Wisconsin politician from an insignificant man into a devastating noun. It warped the country’s economy, stifled its artistic life and stunted its cultural growth. All that, mind you, in the country with by far the better claim on the moral high ground.

Abroad, the Cold War fed the paranoia of one of the great dictatorships of history and gave a bad name to the liberation movements of dozens of colonial nations whose causes Americans might have embraced in a more rational world.

This is by way of saying that the end of the Cold War was truly one of the beautiful moments of history, even if we awoke to a world full of irredentism and post-ideological struggle that took the form of flames rising from Manhattan skyscrapers, a smoldering gash in the Pentagon and a hole in a Pennsylvania farm field.

So much of this struggle is in the memory of those who live among us — memories of episodes like the Berlin blockade, the Berlin airlift and the construction of the Berlin Wall, among many others. We remember these specifics but such memories crowd out the larger triumph, which is far bigger than the victory against Communism.

The collapse of the Berlin Wall brought an end to one of the most terrible eras of history, the time of the tyrants. We have more to celebrate than we think.