Despite unusual official denials here of any troop movements near the Polish border, it seems clear that the Kremlin is heightening its military and psychological pressure on leaders of Poland's Communist Party and independent trade unions.
For the Kremlin, events stand at a crucial turning point.
Western diplomatic sources here think Moscow is trying to avoid the use of Soviet armed force, which they know will end hopes of any progress toward detente for a long time to come.
The West could do little militarily. But incoming President Ronald Reagan could push ahead with a new arms buildup, and West European leaders could firmly put an end to Soviet hopes of dividing them from the United States.
Moreover, the Soviet would have to run a bankrupt Poland seething with hatred for its new masters.
That said, latest Soviet moves close to the Soviet-Polish border apparently have put Warsaw Pact forces in positions and states of alert in which an invasion could be ordered at any time.
According to Western sources here, the alerts and movements of Soviet, Crech, and Hungarian troops are designed to put pressure on Polish leaders and unionists during this week's meeting of the Central Committee of the Polish Communist Party. They do not necessarily signal that an invasion is imminent.
But they do add to the level of Soviet pressure. According to sources here, the East German border with Poland is closed to Western military observers until Dec. 9, to a depth of about 25 miles.
Soviet troops near the Polish border reportedly have been raised from alert level "two" to alert level "six," the highest of all, according to reports from Berlin. In East Germany, Army leave is said to have been canceled -- and the Soviets' 19 divisions in East Germany are at full strength.
Asked about such reports by telphone Dec. 2, the Soviet Foreign Ministry categorically denied them. Usually requests for reaction from the ministry are met with a polite "no comment."
This time, when newsmen called, a spokesman read a statement calling troop reports "rumors" and "inventions." Soviet troops in the trans-Carpathian area (near Poland) were "living a normal life." So were other Soviet forces in other areas. There had been no mobilization, urgent or nonurgent, nor any call for reserves.
Yet Western sources here confirmed "unusual" military activity around Poland. And in Washington, the State Department called in Soviet Ambassador Anatoly Dobrynin for an unannounced meeting Dec. 2 to hear US concern about Soviet intentions.
Other events also indicated Soviet concern. Romanian Foreign Minister Stefan Andrei flew to Moscow unannounced Dec. 2 for what the news agency Tass called a "friendly" talk with Soviet leader Leonid Brezhnev.
East German Premier Willi Stoph was due in Prague to see Czech Premier Lubomir Strougal. SoViet Defense Minister Dmitri Ustinov was in Bucharest, Romania, at a meeting of Warsaw Pact defense ministers.
A sign the Soviets hope backstage pressure plus Soviet economic aid can still prevent the need for an invasion can when Polish radio announced a huge new Soviet hard-currency loan of $1.1 billion for 1981 after talks between the Polish finance minister and the head of the Soviet state bank here recently.
Pravda printed an indirectly but clear warning that Warsaw Pact forces were ready to act against Poland. Pravda did so by reprinting (and thus approving) a strongly worded piece from the Czech party organ Rude Pravo in a recent issue.
A senior Soviet official, Leonid Zamyatin, has told Soviet TV viewers that "millions of dollars" were pouring into Poland from the West to support the new trade unions.
In sum, the Soviets have both laid a basis for invasion and prepared their troops.
As yet unknown is how long Soviet patience can last. If the Soviets conclude they must act, some sources here believe they might do it soon, before Mr. Reagan takes office. But they will almost certainly try to delay for at least a little while longer, these sources think, in the hope that Polish leader Stanislaw Kania can yet restore order both in his party and in volatile, strategic, heavily Roman Catholic Poland.