It was just before 10 o'clock on a warm August evening when Khabas Bekulov's battalion received the order to invade.

Convinced that right was on his side, at exactly midnight, the 21-year-old Russian anti-aircraft gunner crossed the undefended border to the south and into unknown territory.

It was Aug. 21, 1968, and Bekulov was one of 200,000 troops from five Warsaw Pact countries flooding into Czechoslovakia.

The Kremlin claimed that the invading Eastern bloc troops were providing "fraternal support" to the Czechoslovak leadership in a bid to restore order. In reality, it was a reactionary strike aimed at crushing the nascent reforms of Alexander Dubcek's Prague Spring.

By dawn, Soviet tanks had reached Prague, the country was occupied, and Dubcek had been arrested. The soldiers had ended the spring.

Forty years later, as Russian tanks rolled onto Georgian territory this week on another mission advertised as peacekeeping, the images of Russian troops atop tanks stirred memories of that earlier August attack.

As medals and orders are being handed out in the coming days to soldiers who fought in South Ossetia, however, few in Russia will be marking the anniversary of the invasion of Czechoslovakia. On the Defense Ministry's official calendar of key military dates in the country's history, there is no entry for August 1968.

"The official reasoning at the time was that no two socialist countries could go to war with one another — so it was never considered a military operation," said Vladislav Suntsev, who headed a Soviet intelligence squadron tasked with rooting out spies and "counterrevolutionaries."

Now 77, Suntsev, a stolid man who still looks every bit the soldier, lives in the Northern Ukrainian town of Zhitomir. Over the past few years, he has set up a web site dedicated to cataloging information about the 1968 operation — codenamed Danube — from eyewitness reports and media accounts.

"The problem is that, even now, documents relating to the operations in Czechoslovakia are top secret," Suntsev said. "The earliest they'll be released is 2043."

Of all the former Soviet Republics, only Ukraine has passed a law reclassifying the 1968 invasion as a military operation, Suntsev said.

That means that Ukrainian veterans of the operation are eligible for benefits, including discounts on medicine and travel and even early retirement. For the rest of the thousands of Suntsev's surviving former comrades from the former Communist bloc, their participation has slipped through the cracks of history.

What cannot be forgotten are the iconic images of Czech and Slovak students facing down tanks on the streets of Prague and young women in miniskirts taunting equally young, grim-faced soldiers.

High on a mixture of ideological zeal and youthful bravado, the young troops of the Warsaw Pact armies, such as Bekulov's battalion stationed in Poland, viewed themselves as defenders of socialism sent to help restore order.

But as Bekulov's battalion pushed past Prague and toward the Austrian border, Kalashnikovs loaded and at the ready, the hostility of the local inhabitants soon became clear.

Daubed on a fence in one village, the young soldier spotted anti-Soviet slogans. "Lenin, wake up! Brezhnev has gone mad," one said. "For Dubcek, freedom and democracy — against the occupation," read another.

As dawn broke, along with a realization of what had happened in the occupied country, crowds gathered on the streets. Young men shook their fists, and people flung buckets of water at the soldiers from their balconies. The troops were ordered not to accept food or water for fear that they would be poisoned.

"People like me, who deified and idolized the Communist Party, expected that the people of Czechoslovakia would share the same spirit," recalled Bekulov, who now teaches economics at a university in southern Russia. "We were shocked that there was this opposition to our ideology."

Despite the fact that resistance was mainly nonviolent and the Kremlin downplayed any casualties, estimates say the lightning strike by the Warsaw Pact troops cost more than 100 Czechoslovak lives. Suntsev's web site lists the details of over 100 Warsaw Pact soldiers he said were killed.

After being bundled on a plane to Moscow, Dubcek returned to Prague, drained and shaken, and beseeched his compatriots not to fight the invasion.

Back in Moscow, the invasion of Czechoslovakia proved a turning point for many Soviet intellectuals, helping to shape the mindset of the generation that would later push home the reforms of the perestroika period.

Five days after the invasion, on Aug. 25, a group of eight young protesters gathered on Red Square. At exactly midday, they unfurled a banner calling for freedom and a Czechoslovak flag. They were detained within minutes.

While most of the protesters were tried and some sentenced to Siberian exile, Natalia Gorbanevskaya, then 22, was excused from trial to care for her young children. By December, however, Gorbanevskaya had been forcibly confined to a mental institution, where she was kept for over two years.

"Of course, today's war stirs up emotions for me," said Gorbanevskaya, who emigrated to Paris in the 1970s.

The brief protest was a moment of isolated courage, a far cry from the jingoistic demonstrations by Kremlin-sponsored youth groups outside the Georgian and American embassies in Moscow this week.

"Back then it was the totalitarian, communist and imperial Soviet Union. Now it is being done by those who want to return Russia to its previous state," Gorbanevskaya said. "Not just the empire, but also the totalitarian regime."