"What are the Russians going to do in Poland?" everybody asks. But in the nature of things there is no good way of telling.

A far more profitable exercise is to think hard about what the United States and its allies will do if the Russians move. Many course are open and advance consideration is essential.

Most analysts here believe the Russians would like the Polish Communist Party to reassert control over the country. The positioning of Soviet forces around Poland is seen to be entirely consistent with that goal, for the Polish party can restore order only by scaring the Polish people. The threat of a Soviet invasion provides a real, honest-to-goodness menace. It thus deals cards to the Communist leaders in Warsaw.

Few American analysts, however, are confident the Polish Communists can do the job alone. Opposition to the regime runs very deep in Poland. Some opposition leaders -- notably in the church and among intellectuals -- understand the need for moving cautiously. But the independent labor movement, Solidarity, is full of diverse tendencies that cannot easily be managed. The less so as the Solidarity leader, Lech Walesa, does not seem to have an overall strategy.

Moreover, the present Polish leader, Party Secretary Stanislaw Kania, is not a well-known figure in the country. He does not enjoy the personal following that enabled Wladyslaw Gomulka and Edward Gierek to bring order out of the chaos that developed in 1956 and 1970. On the contrary, Kania is highly vunerable to rivals within the party -- notably the former interior minister, Mieczyslaw Moczar, and the former foreign minister, Stefan Olszowski.

Either one of those would be willing to assert discipline, but probably they would have to use force. They might well ask the Soviets for help. The Russians are now well positioned for that eventuality, and the odds are that -- sooner or later -- there will be some kind of Soviet intervention.

The Western allies, in those conditions, could not react directly. No responsible authorities in this country or Western Europe contemmplate military intervention in Poland. On the contrary, it is understood as one of the rules of the game that Poland falls within the Russian sphere of interest. But other steps are open to the United States and the allies, and unless those steps are taken, the Russians, having once again intervened without paying a big price, will be all the bolder in the future.

A show of determination by the United States represents probably the most important ingredient of any reaction. Over the past few years this country has given its reason to doubt its willingness to stand firm against the Soviet Union. Dispelling the impression of American unreliability is a top priority, and the way to do it is not in doubt. Friends and allies will take the United States seriously only when Americans show a disposition to pay the "blood tax," for a return to the draft is a must if the United States expects to organize any serious resistence.

Indirect action harmful to Soviet interests is distinctly possible. Thanks to bad harvests, Russian food stocks are verly low. A cutoff of grain exports would hurt badly, especially if it were done in the context of a general boycott that made it hard for the Russians to buy all the goods and services they need from abroad. The Russians are vulnerable to guerrilla harassment in Afghanistan.

Then there are the various Soviet stooges around the world. Libya is vulnerable. So is South Yemen. If the Russians play hardball, the United States and its allies need to reply in kind. Making life hard for the troublesome regimes in Tripoli and Aden is an obvious thing to do -- especially since pressure can be applied by nieghboring countries.

Finally, of course, a long-term drawing together of the Western allies is a clear requirement. The United States and the Europeans have been slowly drifiting apart. The blame is shared, and there is no need for recriminations here. In any circumstances, a mending of allied ties would be an urgent priority. A Soviet thrust into Poland would only underline the need. Indeed, a new burst of Soviet brutality would promote allied cohesion -- the bit of silver lining in what is otherwise a deep, dark cloud.