Terror then and now: three glittering European cities illustrate the thin line between normality and chaos.

IT WASN'T UNTIL after I got to Prague on August 12, on a vacation, that I realized I had obliquely witnessed a small skirmish in the War on Terror. "Look at that," my mother said, pointing to the departures screen as we changed planes in Brussels. "The flight to London's been canceled--that's strange."

A few hours later, watching Sky News at our hotel, my family and I learned that all hell had broken loose over a reported plot to bomb U.S.-bound airliners. Had we flown via London, we might have spent our vacation sleeping on the floor at Heathrow airport.

It was ironic that this brush with the international struggle against Islamist terror came as we were on our way to visit three Central European cities that witnessed some of the worst struggles of 20th-century totalitarianism. While those struggles seem almost ancient today, it is fascinating to compare the total conflict of the past with the lower-impact fight that absorbs us now.

In the Czech Republic today, the memory of communism and its victims is not what it was when I visited Prague for the first time in 1990, only months after the Velvet Revolution. Back then, most Czechs pretended not to know Russian, which they had been force-fed in the state schools--which created real problems, since most of them also quite genuinely didn't speak English. The hostility toward the Russians was muted but present.

Today, Russian is spoken readily and cheerfully, and the Russians in the Czech Republic are mostly of two varieties: tourists who spend money here, including the nouveau riche who spend quite a lot of it, and guest workers who, after the misery of Russian or Ukrainian provinces, are content with even menial jobs.

Among the Czechs I've spoken with on this and three previous trips in the past five years, none were nostalgic for communism, and all seemed more concerned with the present, with its opportunities and problems, than with the past. Prague, once grim and bare-shelved despite the varied beauty of its architecture, now rivals any other great European city in the abundance of restaurants, souvenir shops, and goods and services; the only major communist relic in everyday life is the lingering tendency to rip off customers in some areas of the service sector. Posters advertising "The Museum of Communism" show a Russian nesting doll with a snarl of pointy teeth.

Yet there are stark reminders that Communist totalitarianism was about murder, not just kitsch. A public art project called "Sculpture Grande '06" is on display in the city; Wenceslas Square is dominated by a genuinely striking piece titled "Kaddish."

The sculpture, by Ales Vesely, looks like a combination of a skeleton, a giant emaciated crow and a crown of thorns or barbed wire; it was, the inscription explained, "symbolically placed above the memorial of Jan Palach and Jan Zajic," two students who immolated themselves in 1969 to protest the Soviet invasion of Czechoslovakia and the destruction of the Prague Spring. The modest memorial itself has a granite slab with images of the two young men, an inscription, "In memory of the victims of communism," and a small wooden cross with a barbed-wire wreath.

Our other two major stops, Dresden and Vienna, were full of 20th-century history of a different kind. If World War II and post-World War II memories have a resonance in Vienna, they have a particular poignancy in Dresden, the city firebombed by the Allies in one of the most controversial chapters of "the Good War."

They also have a particular relevance to the global war on terror: Recently, the bombing of Dresden has been cited by some hawks (such as New York Post columnist John Podhoretz) as an example of the kind of resolve on the part of the Allies that the West lacks today in its confrontation with Islamism. The hawks say the resolve to reduce enemy cities to rubble and inflict massive civilian casualties may be a necessary precondition to victory.

Dresden, like no other place in Europe, drives home the full meaning of this argument. The rebuilt city center today is a tiny island of baroque splendor, resurrected out of charred rubble that is still visible on a patch of land by the island's edge, and surrounded by dreary postwar communist-era construction.

The destruction of Dresden's fabled cultural treasures was accompanied by the loss of 25,000 to 35,000 lives in a horrific firestorm that engulfed the city. And, while Podhoretz writes that both the leaders and the populations of the Allied nations exhibited "a cold-eyed singleness of purpose that helped break the will and the back of their enemies," the fact is that the Dresden bombing, which had dubious strategic and psychological value, was hugely controversial at the time. Many British and American leaders distanced themselves from the raids, describing them as wanton terror. The bombing of Dresden was also a key factor in postwar attempts to suggest a moral near-parity between the Nazis and the Allies--a dubious strategy to emulate.

In one sense, the prosperity on display in Prague, Dresden, and Vienna demonstrates the distance we've traveled from the horrors of totalitarianism. It's unlikely that Islamist terrorism will prove as physically destructive as the beating Europe took from the right and left hands of modern tyranny.

Yet Dresden and Vienna, at least, are reminders of the fragility of civilization. Before the war, these cities were glittering centers of urban life and culture, much as they are now. Today, walking these same streets amidst the crowds of tourists, the shopping, the dining, the museums, it's hard to imagine that all this vitality and prosperity could be turned into ruin and death. But it was, just six decades ago. Who, relaxing in a Vienna cafe or strolling past the gorgeous Zwinger Palace in Dresden in the mid-1930s, could have imagined the destruction that would follow?

Is radical Islamic terrorism today as great a threat to the West as Nazism and then Communism were in their day? Hitler's and Stalin's empires were vastly more massive and powerful. The power of the Islamist terror network is more spread out and amorphous; this time the bombs could come from within. Yet our responses to Islamist terror in some respects have exceeded our responses to totalitarianism.

Returning through Brussels, my parents and I faced new regulations under which no carry-on luggage was allowed on U.S.-bound flights, except for a laptop with no other items in the case and a few essentials in a clear plastic bag. Even the chocolates I had picked up at the duty-free shop at the airport had to be checked at the gate. Back in New York, items that had spilled out of carry-on bags clearly not suited to withstand baggage handling--a pair of sandals, a notebook, what looked like a sandwich in a paper wrap--drifted along on the conveyor belt to nervous laughs from the passengers.

I remembered a comment made a few years ago by the curmudgeonly Arnold Beichman, a scholar and Hoover Institution fellow whom I had gotten to know on my first trip to Prague in 1990. He admitted to a certain nostalgia for the Cold War, at the height of which we did not have to remove our shoes and belts when boarding a plane. Is this a more dangerous world, or a more paranoid one? Or both? None of the "security" measures I saw at the airport inspired a true sense of security, or of anything beyond the appearance of doing something.

But whether of not the London bombing plot had much of a chance of succeeding, the danger is real, and terror could destroy a society just as surely as conventional war. The lessons from Europe's past--the thin line between normality and chaos, the deadliness of totalitarian ideology, the danger of democracies losing sight of their own values while battling an evil empire--remain all too relevant, and the lessons of history offer no easy answers for today.

Cathy Young ([e-mail]) is a columnist for The Boston Globe.