THE OLD East Europe, supposedly rescued once and for all from Moscow's grasp, suddenly isn't so sure. It sees Soviet hard-liners gaining on reform and it wonders whether the developing chaos may embolden local old-style Communists, upset economic transfers, send a spill of refugees and otherwise tend to destabilize the region that now prefers to be called Central Europe. Of special concern is the possibility that a troublemaking Red Army will delay or burden the repatriation of Soviet military units, especially from Poland. Poland does not have a formal agreement to guide the return of the 50,000 foreign soldiers (plus families) still on its soil. Hungary, Czechoslovakia and the former East Germany fortunately do.

The Soviet old guard, civilian and military, nurses a bitter, wounded pride. Its members are pressing the claim that Mikhail Gorbachev "lost" Eastern Europe. They are foolish and wrong. The Gorbachev foreign policy revolution that dissolved the Soviet bloc vastly strengthened Soviet security and provided it a precious opportunity -- one it may now be kicking away -- to renew Soviet society.

The immediate effect of the old guard lament is not so much to threaten to bring the region back under Soviet sway, however. It is to challenge Mr. Gorbachev's power at home. The Cold War meant the forcible division of Europe, and Germany. To imagine that even some lesser part of all this could be restored is to overlook the backlash such an attempt would surely stir in Europe and beyond. Armed resistance would be certain. East-West political relations would go into the deep freeze. NATO would suddenly have a clear mission again; the Warsaw Pact, already a wreck headed for formal dissolution by April, would have not the slightest comparable chance of revival. The Soviet Union would have to abandon hope of access to the global economy for at least a generation.

To say that the worst is unlikely is not to say that the Soviet army, by pushing the Kremlin leadership, or the Kremlin, following its own hard line, could not cause plenty of worry and trouble in the neighboring region. The West cannot respond to every bump and jostle, but it also cannot fail to make sure the Soviet authorities understand how completely unacceptable it would be for them to mess up Central Europe and how immense and certain would be the costs to the Soviet Union itself. It is bad enough that Soviet troops should fire on and lean on people in the Baltics and elsewhere who are, however involuntarily, Soviet citizens. It is especially offensive that anyone would try to manipulate the presence or transit of Red Army units to intimidate the democratically elected governments in the former Soviet empire.