WASHINGTON -- Twenty years ago, early in October, I found myself in East Berlin observing one of modern history's most incredible events.

The rulers of East Germany had called one of their regular demonstrations in favor of their particularly grotesque Communist regimen. There they stood, the leaders of this Potemkin police state, awaiting the usual applause in a lineup before East Berlin's Rotes Rathaus or Red City Hall.

It was a lovely fall day, and I was standing protectively near the back of the crowd when "it" started. The crowd of East Germans began to hiss and boo at their "leaders," to shake their fists, and finally to laugh at them and mock them. The lineup of cold-blooded men physically cringed. This had never happened before.

I thought to myself that day, "It's over; it's finally all over." And it was. I went back to the Grand Hotel on Unter den Linden, the East's premiere luxury hotel, and had a glass of wine, which had the contradictory effect of only sobering me up.

Within a month -- on Nov. 9, 1989 -- the Berlin Wall came down in an outburst of both rage and hope, and Easterners from north to south poured into the West, as Soviet Communism began its final fall. The 20th anniversary of that extraordinary event will be celebrated in a Festival of Freedom at the Brandenburg Gate in Berlin this Nov. 7-9, but while we know WHAT happened that night two decades ago, there is still a great discussion as to how and why.

Some say the East Germans simply opened their grim and grotesquely armed checkpoints between East and West. Many say that the events were due, of course, to new Soviet President Mikhail Gorbachev's policies of "opening" to the world. Large sectors here in Washington persist in giving all the credit to Ronald Reagan for the fall of Communism -- he terrified the Russians with his rearming, this argument goes.

In fact, party officials both in Moscow and East Berlin were totally unprepared for their own collapse. Meeting that same Nov. 9 in Moscow, the Soviet Politburo did not even discuss Berlin, but received a panicky report about collapse in the Baltics. And party officials in East Germany explained patiently to me that October that they were working on a new "social concept" of a reformed socialist state to be put into effect in November -- but there was no longer any time for such belated "planning."

On the surface, the movements of people were all accidental. That day an East German official, holding a press conference to give out new government travel policies, inadvertently announced that crossings to the West would be opened "without delay." A respected TV anchorman in West Berlin picked up that promise on his show, and word was passed from house to house and from person to person. But accidental?

From what I saw in those days and years, all during the '80s, the fall of the Soviet state and the freeing of Eastern Europe had become unavoidable. As I wrote then: "What happened after the high drama of reunification ... can now be seen as less accidental than inevitable. The West Germans substantially underestimated, as did most of the West, the disastrous shape of the Eastern economy. It also did not expect that the Soviet market, upon which East Germany depended, would also collapse, leaving a void that could not quickly be filled."

Four years later, I would go to Siemensstadt or Siemens City, in what was a suburb of East Berlin. There, the gigantic West German electronics empire, Siemens, had taken over plant after plant successfully. But managers also told me that, even though they had gone for years to East Germany's annual Leipzig industrial fair and thought they had a pretty good idea of Eastern industry, in fact they knew nothing about its sobering reality. East Germany's was an "isolated system" that brought about its own doom, and it was more like a "developing country" than a developed one.

For the next few years after the Wall fell, you heard nothing but complaints from both Easterners (the "griping Easterners," the Westerners called them) and Westerners (the "know-it-all Westerners," as the East Germans called them). Eastern salaries remained low for years, and 40 percent of the vote continued to go to the Communists. Men and women who had struggled to open those jammed gates now complained that they had no "identity."

Later -- on the 10th anniversary of the fall of The Wall, and beyond -- Western politicians would understand better why the Eastern assimilation to the West took so long. The Easterners had been politically weaned on both Nazism and Communism, and both had failed them. It would take a generation.

Meanwhile, the American administration immediately responsible, that of President George H.W. Bush and Secretary of State James Baker III, consciously practiced the very best diplomacy -- on the surface, at least, they took no part in the drama of the Wall. "I won't dance on the wall," President Bush said famously, and Gorbachev appreciated this, never blaming Washington for what happened.

Today, on this 20th anniversary, there are still many complaints about reunification on both sides of the disappeared wall -- but they are increasingly unimportant in light of today's highly successful united Germany.

Today's Germany has no territorial claims on anyone and only friends as neighbors. Its democracy has strengthened since 1989. Germany, including its Eastern states, has been totally integrated into Western structures, with Germany at the center of a European Union that now includes almost all the formerly Soviet-dominated states of Eastern Europe. Almost alone among the aggressor states of the 20th century, Germany has paid enormous sums to the survivors of its terror, thus establishing new norms of international behavior.

Who would have dreamed it?