IN DECEMBER 1990, A FEW WEEKS AFTER MY RETIREMENT, I HAD flown to Germany to join Jonna in Berlin. She was on temporary duty in Moscow, so this quintessential espionage Ground Zero of the Cold War seemed an ideal place for us to meet.

But I experienced a moment of panic when I received word that her flight was diverted from the airport in the former West Berlin to Schönefeld in the former East Germany. Hell, I thought, who screwed up by sending her into the DDR? But then I relaxed. The Deutsche Demokratische Republik no longer existed. Germany had been reunited under a truly democratic form of government. The former Soviet client states of Eastern Europe were rapidly breaking free of Moscow’s imperial control.

Very early on Christmas Eve morning, we walked from our hotel near the Ku’damm all the way to the Brandenburg Gate, where the stark tyranny of the Wall had first been breached and the death of Communism had become inevitable. Even this early on a freezing winter day, the hungry soldiers of the Soviet Army had set up their flea market in the Potsdamer Platz in front of the war-scarred arches. They were peddling hammer-and-sickle badges, regimental insignia, and their gleaming Red Army belt buckles for a few marks so they could afford a German breakfast, a piece of wurst and a few potatoes for supper. We bought several belts and a couple of insignia patches, then tried on their steel-gray fur hats and took pictures of each other.

Next we walked through the gap in the wall and down the east side, examining the graffiti and primitive Utopian art plastered on the concrete all the way to Checkpoint Charlie. We immediately noticed the inescapable drabness of East Berlin, which stood in gaunt contrast to the holiday prosperity of the West, even a full year after the Wall had been opened.

The people had the same furtive, downtrodden expressions I had first encountered in Moscow in the mid-seventies. Communism had not simply deprived them of material wealth, but it had also crushed their spirits. Most of the men and women with whom we mingled on the way to Unter den Linden had never known a life free of the arbitrary cruelty of the Gestapo or the Stasi. The German Federal government had just announced plans to demolish all traces of the hated Wall. I hoped that they would leave at least one section intact as a bleak memorial to all those people who had suffered under totalitarian Communism.

Jonna and I were married in July 1991. Jesse Lee, her first child, and my fourth, was born on September 19, 1992, and Jonna retired from the CIA four months later.

We returned to Berlin in the summer of 1998 and found the changes in the former East Berlin astounding. We counted more than 150 hammerhead construction cranes radiating out from the Potsdamer Platz, marking the biggest construction boom in European history. Berlin will be reinstated as the capital of Germany in the year 2000. Fortunately, the local government did decide to preserve one small segment of the Wall, not far from Checkpoint Charlie.

Given the undeniable prosperity of Berlin, it would seem that the world has become a safer place now that the West has won the Cold War, and the CIA and its sister services have defeated the KGB and its many allies.

But such optimism may be unfounded.

The 100,000 people who once worked for the KGB did not simply retire to their dachas and take up gardening. True, many are forced to maintain vegetable plots, but their motive is survival. The SVR, or Russian Foreign Intelligence Service, still spies on the West. Alumni of the KGB have blatantly sold themselves, both at home and abroad. Reportedly, members of the elite Grupa Alpha antiterrorism unit of the former KGB Seventh Chief Directorate are now the bodyguards and enforcers of Moscow’s leading Mafia bosses. And, of course, Russia still possesses one of the world’s largest arsenals of nuclear, chemical, and biological weapons.

I cite these harsh realities whenever people ask if there is still a valid reason for the United States to maintain an extensive, active, and expensive intelligence community.

Yes. Vigilance is, indeed, the price of liberty.