The role of Poland's Communist Party, which had become a symbol of oppression to large numbers of Poles, has been deliberately obscured under the martial-law government, according to well-informed sources familiar with the decision to crack down on the independent Solidarity labor union.

Although Poland is now being directed by a 21-man military council, and soldiers appear everywhere -- directing traffic, delivering news broadcasts, supervising factory production -- the Communist Party Politburo, which is the party's top policy-making group, is said still to be running the country with the military receiving orders from it.

It appears that the decision to submerge the visible role of the party was a tactical one. Poland's Army, composed largely of draftees, is a source of national pride and trust by the population, in marked contrast to the party.

In the first days after the imposition of martial law, the strategy of seeming to place the Army above the party was emphasized by placing the Polish flag atop the party's Warsaw headquarters in place of the red Communist flag. Today, the party flag reappeared again beside the Polish standard.

Just as the tactics adopted on the relationship between the party and the Army appear to have been carefully thought out, so, too, were the mechanics of setting the martial-law rule in motion.

According to these sources, the orders putting martial law into effects had already been issued -- and indeed the crackdown was well underway -- when the country's largely figurehead Council of State was summoned to formally authorize the measure.

The council does have as one of its constitutionally vested responsibilities the power to impose martial law. Its proceedings during the decisive hours of last weekend, recounted here by an authoritative source, provide some insight into who actually took the decision to mobilize Poland's Army against the country's own citizenry.

Preparations for the declaration of a state of emergency to stop the independent trade union Solidarity and restore the party's authority had been under way for many months, even before the intense face-off between the union and the authorities last spring over the beating of some Solidarity officials in the town of Bydgoszcz.

The turning point came Dec. 3, when Solidarity's regional leaders met in Radom. Enraged over the government's use of force the day before to clear striking cadets from the Warsaw firefighters' academy, the union leadership approved seven tough demands calling for government action on a number of points ranging from economic reforms to greater access to the media -- matters on which union officials accused the government of foot-dragging.

The Solidarity leaders also threatened a general strike if the government proceeded with the Communist Party's call for adoption and enforcement of emergency-powers legislation.

Final preparations for martial law were then begun and party activists received detailed instructions, according to informed sources.

Soviet Marshal Viktor Kulikov, in charge of Warsaw Pact forces, is reported to have been in Poland for several days before martial law was imposed and is thought to have supervised the preparations.

By this account, the final decision to move was taken only last Friday, the first day of a two-day meeting of the union's national commission in Gdansk. That meeting went on the next day to approve Solidarity's most daring declaration against Poland's Communist authorities, calling for democratic elections and mass rallies and threatening a general strike.

The call to Council of State members came at 12:15 a.m. Sunday, well after the initial order to march had been given. The 14 members -- two were on vacation -- assembled in the State Council Building at 1 a.m. for a meeting that lasted two hours.

Also present were several Polish Army generals, but not Gen. Wojciech Jaruzelski, Poland's prime minister and defense minister and chairman of the Communist Party. The council members reportedly were presented with the decree that had been drawn up in advance declaring martial law.

The atmosphere was described as tense with the thought that what was happening would be a monumental step for Poland, the first time in its postwar history that the introduction of martial law was even being considered.

In the course of the meeting, the question was raised of dissolving the party in favor of an entirely military regime. The purpose would have been to exploit the Polish public's trust in their Army. But this course was rejected.

Finally, when the decree came to a vote, only one council member, Ryszard Reiff of the Catholic political faction Pax, disapproved.

Strictly speaking, when the Sejm is in session, as it had been at the time, it is the body under Poland's constitution that should have taken the decision to impose martial law, not the Council of State. The council is empowered to impose martial law only in the period between legislative sessions.

It is a legality that it certainly seen now to be a moot point.