NEWS ANALYSIS : Moves in Moscow Bring Early Chill to Eastern Europe : Reaction: The end of ‘Prague Spring’ is recalled. But Czechoslovak leader now sees change as irreversible.

Scenes of tanks thundering through Moscow after the fall of Mikhail S. Gorbachev and his age of reform have sent an unseasonable chill through Eastern Europe, where past victims of Stalinist aggression fear they are once again at the mercy of the Communist giant to the east.

The Kremlin coup that has ousted the most influential leader of the late 20th Century was carried out by the same military and KGB hard-liners who have been lamenting the escape of Eastern Europe from the Soviets’ political grasp.

Their toppling of Gorbachev is the realization of the emerging democracies’ worst fears, stirring concern that the Kremlin might resort to desperate acts to recover international supremacy, like the invasions that quashed the Hungarian Uprising of 1956 and the “Prague Spring” of 1968.

A conservative crackdown on independence-minded Soviet republics could also set off a refugee wave and further batter the struggling economies of the newly liberated East. Many fear that the resurgence of hard-liners in Moscow will strengthen the hand of Communist aggressors in Yugoslavia and breathe new life into the ailing ideology throughout what used to be known as the East Bloc.

Yet much has changed in the scant two years since Gorbachev’s “new thinking” in foreign policy granted Eastern Europe its freedom, setting in motion the anti-Communist revolutions that swept from Poland to Romania in 1989.

As Czechoslovak President Vaclav Havel commented upon hearing the stunning news of Gorbachev’s fall, “It’s not possible to turn back the wheel of history.

“We are convinced that the developments on the road toward democracy are irrevocable, even in the Soviet Union, and that democratic forces will celebrate victory in the end,” Havel predicted confidently, but with a word of caution.

Noting that the Soviet crisis came just before a solemn date for his own nation--the Aug. 21 anniversary of the Soviet-led invasion of Czechoslovakia 23 years ago--Havel warned that Eastern Europe should not “take the latest developments in the Soviet Union lightly and fall victim to any kind of illusion.”

The “illusion” he referred to may be any sense that Eastern Europe could deter a Red Army invasion on its own. Since the collapse of the Warsaw Pact alliance, the region has been left in a military limbo. The reform-minded states have severed formal ties with the Kremlin, but their overtures to NATO have been resolutely deflected as premature.

While Eastern Europe is militarily and economically weak, an outright offensive by the Kremlin to force it back into the Communist fold is considered unlikely. The new Soviet leadership has its hands full with Baltic and Central Asian secessionist movements, as well as with widespread social and labor unrest that even eroded military discipline.

The 1989 revolutions that spun six Eastern European nations out of Moscow’s orbit led to free elections that have restored full sovereignty and fueled a free-market reform movement in each state.

“The removal of the Iron Curtain and the reunification of Germany created an irreversible situation in Europe,” observed Laszlo Varga, a leader of the Christian Democratic People’s Party that is part of Hungary’s governing coalition. “It is inconceivable for the Soviet Union to extend its power toward Eastern Europe.”

Both Hungary and Czechoslovakia celebrated the departure of the last Soviet troops from their countries in June, and the Red Army now has no remaining foothold it might use to move in and restore the link with Moscow.

East Germany has been wholly absorbed by West Germany and the powerful NATO alliance in which it is bound, making Soviet recovery of that former East Bloc front line virtually impossible without a colossal confrontation with the West.

Bulgaria and Romania are still ruled by Communist successors, and their Black Sea ports may be attractive from a military standpoint. But the political and economic chaos gripping those countries would likely deter even the most radical generals from expansionist moves.

Swift political change in the Balkans has so far resulted mostly in widespread labor and social unrest, which perhaps contributed to the Kremlin conservatives’ decision to act to avoid total collapse of their own economy.

Poland, where nearly 50,000 Soviet soldiers are still stationed, might be seen as more at risk than its former allies because of its strategic Baltic Sea location and its proximity with the secessionist Soviet republics of Lithuania, Latvia and Estonia.

“I think we should shudder a bit,” commented Polish historian Jerzy Holzer. So far the Soviet upheaval has only affected domestic affairs, “but if they want to show the world that the Soviet Union is still an empire, Poland is Point No. 1 because of the presence of Soviet troops.”

But even in Poland, few expect the Kremlin to resort to aggression for a lost cause. While the Soviet Union has lost key agricultural and industrial supplies as its former satellites redirect trade toward the West, the region’s dependence on Soviet energy supplies has made it more of an economic liability than a colonial asset.

“Direct military action can hardly be envisaged,” one government source in Warsaw said shortly after the news of Gorbachev’s ouster.

The size of the Soviet military force in Poland and Germany, where 273,000 Kremlin troops are still stationed, might seem intimidating. But the troops are in the process of withdrawal and therefore in a poor state of readiness for any assault, said Francois Heisbourg, director of the International Institute for Strategic Studies in London.

“It would make no sense to freeze the withdrawal. This would make relations with Poland and Germany untenable,’ Heisbourg said. “And anyone will tell you that a retreat is the hardest operation to carry out.”

Janos Kis, president of Hungary’s main opposition party, the Alliance of Free Democrats, also said that Kremlin military aggression is unlikely.

“In the short run, the most negative influence of the Soviet change may be on the Hungarian economy,” Kis said. “But we shouldn’t be afraid that the Soviet leadership will try to gain back the Eastern European countries by military force or threat. They simply do not have the power to do that.”

Western military attaches refused to assess the potential risk of invasion so soon after the Soviet leadership change.

Yet many in Eastern Europe are still fearful of the political and military powerhouse on their eastern border.

“We feel insecure because all of the reforms and democracy have just started here, and they are very weak at the moment,” observed Endre Barcs, a Hungarian Radio correspondent covering international affairs who still vividly recalls the brutal 1956 invasion he witnessed when he was 10. “If a very conservative party gets into power in the Soviet Union, we have to be very afraid, and I think that is the opinion of most people in Hungary.”

While political leaders were hesitant to make bold forecasts of what might be in store for their own countries should democratic advances in the Soviet Union be rolled back, a consensus was forming that the Kremlin was too distracted by the domestic turmoil that inspired the overthrow of Gorbachev to commit the resources and attention that would be needed to reconquer Eastern Europe.

Anti-Communist sentiment throughout most of Central Europe--the geographic description now preferred by Hungary, Czechoslovakia and Poland--has intensified in the wake of the Soviet retreat, which has left the region grossly polluted and mired in the faulty economics of central planning.

The broad resentment of Moscow that has set in would make it doubly difficult for Soviet authority to ever re-establish itself in the region with anything short of a massive military occupation.

More worrisome for the fledgling democracies that elected non-Communist governments only last year is the prospect of an even more thorough collapse of the Soviet trade network on which each of the economies remains heavily dependent.

Hungary and Czechoslovakia were both poised to sign major trade agreements with individual Soviet republics. The republics were being given more autonomy in foreign economic relations under the new Union Treaty, whose signing Gorbachev was to have overseen today.

The hard-line resurgence in the Soviet Union also feeds Western fears that Eastern Europe remains too unstable a region in which to invest, said Josef Alan, director of the Charles University Institute of Social and Political Sciences in Prague.

“Regardless of how they turn out, these developments will strengthen the voices in the West that are against supportive policies toward Czechoslovakia and all of Eastern Europe,” warned Alan.

The overthrow of Gorbachev underscores the view that reforms in once-Communist countries are “still on shaky ground,” Alan said. He considered recent outbreaks of violence in Yugoslavia an inducement to Western businessmen to hold off on projects that are crucial to the region’s recovery.

Yugoslavia has been torn by ethnic and political confrontation between Communist-ruled Serbia and the nationalist governments of Croatia and Slovenia, which declared independence on June 25.

Some see the dramatic turn of events in the Soviet Union as a disturbing green light for further aggression by Yugoslav Communists.

The Supreme Council of Croatia, headed by President Franjo Tudjman, called the Soviet leadership change a KGB-supported “putsch” with significant international consequences.

“There is a real danger that in coordination with those circles in the Soviet Union, a similar scenario will be tried in Yugoslavia,” the Croatian council stated.

Yugoslavia’s collective presidency had no immediate comment on the ouster of Gorbachev.

The Soviet government issued an unusually harsh statement on the Yugoslav crisis last week, warning the West not to intervene militarily and saying such action could spread the conflict throughout Europe.

“Yugoslav hard-liners will be strengthened by this development, but we will not see any wholesale revival of communism in Eastern Europe,” said Michael Stuermer, director of the Research Institute for International Policy and Security in Ebenhausen, Germany.

Others refused to rule out the possibility that the embattled Communists would make one last try.

Predicting a reinvigorated struggle for survival by defeated Communist parties, the leader of Poland’s Conservative Party said the Yugoslav and Soviet developments pose the threat of a new cycle of global confrontation that could even escalate into world war.

“The situation in the world is very dangerous because of the Yugoslav events,” said party leader Jerzy Korwin-Mikke. “The Communists in Yugoslavia will now raise their heads, and the world will no longer take much notice.”

Poland is to hold elections in October for its 400-seat Sejm, or lower house of parliament, which will likely provide the first test of the surviving Communists’ strength in the era after Gorbachev. Bulgaria also plans fall elections, but no firm date has been set.

Political analysts in Warsaw worry that the revamped Communist Party could post significant gains during the election, as Poles may feel safer in a politically diverse buffer state than as the pro-capitalist front line against a volatile superpower.

Polish President Lech Walesa seemed to be reassuring his people that their turn toward democracy and capitalism was safe from any Soviet incursion. He vowed that in Poland, “we will continue to build democracy and reform our economy.”

Government leaders from Poland, Czechoslovakia and Hungary said they would coordinate any efforts deemed necessary to safeguard their borders, as well as to deal with any influx of refugees should Soviets begin to flee a more authoritarian regime.