IN many ways, the sign on the shop window in Prague, ``Gorbachev is with us,'' summed up better than anything else the stunning changes that have swept Eastern Europe in the past year. Such a sign would have been impossible just a short time ago, where the Soviets for so long have been synonymous with repression and dictatorship and where they have crushed at regular intervals - directly or indirectly - local attempts to reform and liberalize: East Germany in 1953, Hungary in 1956, Czechoslovakia in 1968, and Poland in 1981.
These were historic events in Eastern Europe, but they were all isolated phenomena, never spreading beyond each country's borders. They ended the same way, in life returning to ``normal,'' to stagnating societies headed by Stalinist regimes propped up by Soviet might.
For a long time, Eastern Europe was one of the most stable regions in the world. Its leaders stayed in power, seemingly forever. Change was measured in very small steps - a passport for someone who had opposed the regime for years, an unusual article, a new film, a private shop.
But this year, one leader after another - in Poland, Hungary, East Germany, Czechoslovakia, Bulgaria, and Romania - fell to popular demands for reform. Throughout the region, the talk is of market-oriented economies, free elections, an end to Communist monopoly on power, even an end to Communist rule itself.
Only a short time ago things were much different. In Czechoslovakia, the period after the tragic invasion of 1968 resulted in exceptional repression under the name of ``normalization.'' Valtr Komarek, the leading economist and the new first deputy prime minister, has called the regime during those years a ``fascist dictatorship'' and compared it with the last 15 years of Francisco Franco's regime in Spain.
In Hungary under Janos Kadar, the political and economic situation was a little brighter. But in East Germany under Erich Honecker and in Bulgaria under Todor Zhivkov, there was only darkness. And as long as Leonid Brezhnev ruled in Moscow and the Brezhnev Doctrine of limited sovereignty within the East bloc was still valid, there really was no chance for change.
Something different was going on in Poland, however. The free trade union Solidarity had been founded in the summer of 1980 only to be suppressed in December 1981, when martial law was imposed and Polish troops did the job for Brezhnev.
With Solidarity, however, the seed that led to the changes of 1989 was planted. For, as Timothy Garton Ash writes in his book ``The Uses of Adversity,'' the Solidarity revolution transformed the ``dissident'' minority into a ``dissident'' majority. It was a ``revolution of consciousness,'' which did not change institutions or property relations, but ``people's minds and attitudes.''
But Solidarity survived many dark years underground, because Poland itself could not survive without it. Last April it was legalized and in September a Solidarity-led government was formed with the first noncommunist prime minister in Eastern Europe since the war.
This remarkable turn of events paved the way for the dramatic changes this fall in East Germany, Czechoslovakia, and Bulgaria.
But Solidarity could not have done it alone. It had some help. In 1985, Mikhail Gorbachev came to power in Moscow. His tacit approval of the changes in Poland served as a signal to the people of Eastern Europe that Mr. Gorbachev would allow reform because he wanted it in his own country. For the first time, a Soviet leader became an ally, not an enemy, of those in Eastern Europe who wanted change.
And when change came, it came fast. ``The old system was so rotten that once the Soviet support vanished, it all collapsed like a house of cards,'' says a Western diplomat in Sofia, Bulgaria, with long experience in East Europe.
Still, he talks of the ``total shock'' that a man like Bulgaria's Zhivkov, who had ruled the country for 36 years as a one-man dictatorship, could so easily and so swiftly be overthrown.
And the changes are remarkable, even difficult to comprehend, because it was all so impossible just a short time ago.
It was after midnight, just a few weeks ago, that a gray-haired man with a big mustache and a warm smile walked home through the empty streets of Prague. He was exhausted after weeks of almost no sleep, but he was also happy, because that day he and the opposition group Civic Forum had won. Jiri Dienstbier knew that his life would change dramatically: The next day when Czechoslovakia's new government would be announced, he would become foreign minister.
``It's all so absurd,'' he said and laughed. ``Imagine, only a month ago, things were so different. They had even shut off my phone.'' And he shook his head and laughed again.
He had wanted change back in 1968, when he was a leading journalist. As a Communist, he supported Alexander Dubcek's concept of ``socialism with a human face'' and he was one of the victims when the Soviet troops marched in. For the next 20 years, Jiri Dienstbier was a nonperson, hounded by the police and jailed for several years after signing Charter 77 on Jan. 1, 1977 - Eastern Europe's most-important human rights manifesto since World War II. He still managed to put out an underground newspaper and meet foreign reporters in his apartment off Wenceslas Square.
But how absurd it all was did not quite hit him until the day he became foreign minister and his old employer at the heating plant, where he had worked for years as a stoker, told him that he could not leave immediately, because there was no replacement.
Once in office, a couple of days later, he immediately went to the border with Austria to cut down the barbed-wire between the two countries together with his Austrian colleague. Then he flew to Moscow to negotiate the withdrawal from Czechoslovakia of the Soviet troops that in 1968 had crushed his dream.
For Jiri Dienstbier, life has truly changed. There are similar examples in other Eastern European countries. In Poland, the former dissidents now sit in parliament, and Jacek Kuron, the man who started it all back in 1975 with the Workers Defense Committee (KOR), is now labor minister. Adam Michnik, another dissident legend, is editor in chief of the Solidarity daily and recently interviewed Soviet Foreign Minister Eduard Shevardnadze.
In Hungary, Imre Nagy, the executed leader of the 1956 revolution, has now been properly buried with full honors. The country is well on its way toward free elections in the spring.
Romanians overthrew and executed Stalinist dictator Nicolae Ceausescu and his wife, while cracking down on Ceausescu's hated Securitate secret police.
And between the two Germanys, the Berlin Wall - the symbol of the divided Europe and of the cold war - has been opened.
Change has not yet reached everyone in Eastern Europe, however. Nonaligned Yugoslavia, which under Josip Broz Tito was the leader of reforms, is today fighting economic stagnation and ethnic strife. And Stalinist Albania, Europe's poorest country, continues its go-it-alone policy.
No one can say if the winds of change will continue to blow in Eastern Europe. With every day, however, the changes become more permanent. Every day, a backlash seems more unlikely, even if Gorbachev were to be ousted. By now, events seem to have gone too far to turn back.