Vienna — The quiet - but large - hand of the Soviet Union can be seen behind the crackdown on Polish protesters following the outlawing of Solidarity.
As Moscow sees it, Poland's leader Gen. Wojciech Jaruzelski is the last ''Polish card.'' Any further political reshuffle (of which there have been a half-dozen since August 1980) is no longer considered an alternative.
It suggests the Soviets, in effect despairing of the Polish Communist Party, are instead placing total reliance on the Polish armed forces as the only potential guarantor of stability on the Soviet's northern gateway to Western Europe.
In the gloomy calculations of observers, the Polish situation carries dangerous implications. Should the Polish military prove unable to cope, and martial law fail to induce national stability, then - in the last resort - the Soviet Union might decide there was no option but to use their own forces, say longtime observers.
General Jaruzelski's own position obviously is growing increasingly difficult - less from internal disorder than from the external tensions between the Soviet Union and the United States.
The swiftness with which the new union plan was finally drafted and voted automatically into law by parliament was out of character with the stand Jaruzelski has repeated regularly since December. The 1980 agreements with Solidarity gave ''decisive'' importance to the return to genuine self-governing trade unions.
The Soviets still, quite clearly, firmly support Jaruzelski as head of the Army and the Military Council that took over last December and as Communist Party chief. But their reliance now counts almost exclusively on his military capacity.
This week's message from Soviet Defense Minister Dmitri Ustinov, on the 39th anniversary of the modern Polish Army, reinforced this impression. ''The Polish People's Republic, as a state member of the Warsaw Pact can be certain of the full support (of) and help from the Soviet Union,'' he said.
It was a gesture significantly addressed exclusively to the armed forces. The absence of any allusion to the civil authority was noticeable, even considering that this was an Army occasion.
It appears beyond doubt that the Soviets have adopted a strictly realistic view that, if the general, with the whole military security machine under his control, cannot bring peace to Poland, there is no other Polish means of doing so.
Recent Soviet comment - including the charge by President Leonid Brezhnev Oct. 12 that the West has launched a ''psychological war'' against the communist bloc - carries strong implications of a significant change in Moscow's thinking and its patience with Poland. The wait-and-see attitude toward the Reagan administration is over, according to this reading of Soviet intentions.
The result, it is said, is that the Soviets have concluded that Ronald Reagan is bent on superiority in every field vis-a-vis the Soviets and that the latter, therefore, must look more to the security of ''their own house.''
The shift in Soviet thinking seems to have come quite recently. A month before martial law there still was a chance - in Jaruzelski's November meeting with Poland's Roman Catholic primate and Solidarity leader Lech Walesa - for the leadership to take some concrete step toward conciliation and cooperation between the authorities and society.
After martial law, the Soviets still seemed to be agreeing with Jaruzelski's insistence on some sort of ''dialogue'' or accommodation with Solidarity. That, in fact, seemed to remain the case until a month or so ago.
They appear then quite suddenly to have changed their mind and the hurriedly contrived demise of Solidarity - without meaningful consultations with Lech Walesa or anyone else having taken place - was the evident result.
The general is surely as well aware as anyone that Kremlin estimates of Polish affairs are conditioned by what it now sees as its strategic interests between East and West.
''Socialist fraternal assistance'' has been an option agreed between Warsaw and Moscow since the crisis began. The restraint in its use till now does not mean it is forever precluded.