A French photographer arrived in Poland over the weekend breathless and excited. His office in Paris had told him that a Soviet invasion was expected at any moment, indeed may already have gotten under way. Disguised as a tourist, his job was to film the carnage in the streets.

The scene that awaited him in Warsaw came as a surprise. Young couples were walking hand in hand in the sunshine. A crowd of tourists watched the changing of the guard at the tomb of the unknown soldier. Families lined up patiently for ice cream and children played happily in the park.

As a picture of normality, it contrasted sharply with the image of rumbling tanks and heroic resistance fighters that had already formed in the photographer's mind.

It also showed that in a world filled with speculation about Soviet intentions toward Poland, the calmest place to be is Poland itself.

With the exception that winter has given way to spring, the atmosphere in Warsaw is like a flashback to November and December.

Then, too, following a bruising round of strikes, a tentative truce was in force between the communist authorities and Solidarity, the independent trade union.

In the West, there were reports of Soviet troops massing on the Polish frontier ready to move at any moment. Few Poles took much notice and, as it turned out, nothing happened.

If that previous scare proved anything, it is that it is very difficult to read the Kremlin's innermost thoughts. Spy satellites can pick up signs of troop movements but they cannot eavesdrop on meetings of the Soviet Politburo to decide what is to be done with those troops.

One reason for the relaxed attitude taken by most Poles toward the supposed threat of invasion is that it is difficult to envisage what the Soviets are supposed to do with their tanks. As a Polish journalist remarked: "What people in the West seem to forget is that the Soviets have been here for the last 36 years already -- and it hasn't done them much good. Sure, more of them can come, but they will be confronted with the same situation."

In the meantime, the Soviet Union can try to exert psychological pressure on the Polish leadership and people. Since this pressure takes the same form as preparations for military intervention -- troop movements, critical press articles, and so on -- it is impossible for the outsider to distinguish one from the other.

In Czechoslovakia in 1968, the Soviets managed to influence the internal political struggle within the Communist Party. They could, of course, do the same here but it would not resolve the basic problem, which lies in the determined resistance to authoritarian rule by a united working class.

The very real threat of a general strike last week demonstrated that Poles are prepared to work only on the basis of dialogue and democracy. In the face of massive popular resistance, the old strong-arm methods of government just do not work.

That lesson may not have gotten home to Moscow yet, but there are signs that it is being understood by an increasingly large number of Poland's own leaders.

The violent incidents in the northern city of Bydgoszcz could prove to be a turning point in the attitude of the Polish authorities. For several days after the affair, in which plain-clothes policemen are alleged to have beaten up Solidarity activists, it was still possible for the ruling Politburo to take a tough stand. But public opposition was so strong that it became necessary to resume solving disputes by negotiation.

The violence in Bydgoszcz caused much soul-searching among workers on the Central Committee, who made it clear they would oppose any confrontation with Solidarity. Local union branches and basic Communist Party organizations started cooperating more closely with each other.

Viewed solely in the Polish context, this development is encouraging because it breaks down the barriers of mistrust and suspicion between the union and the party at local level. But seen from Moscow's viewpoint, it could be interpreted as an alarming sign of the disintegration of the Polish Communist Party.

The Polish party leader, Stanislaw Kania, realizes that the situation within the Communist Party is of utmost concern to the Soviet Union. It was, after all, the alleged danger of "liberalism" in the party -- rather than a workers' rebellion -- that brought the Soviet invasion of Czechoslovakia.But Kania also knows that the party must change in order to retain the support of its rank and file.

His problem now is how to persuade the Soviets that it is in their interests to accept reforms. His wants to proceed step by step. At the last Central Committee meeting, he resisted moves to evict hard-liners from the Poliburo, preferring instead to expand its membership later with some of his own supporters.

It was for this reason that a reputed hard-liner, Stefan Olszowski, was sent to represent the Polish party at this week's Czechoslovak party congress. Olszowski's presence in Prague appears designed to reassure the Soviet Union that conservative pro-Moscow politicians still retain some influence in the Polish leadership.

In the meantime, steps are being taken to resolve some of the main disputes with Solidarity. A law restricting censorship, one of the main pillars of most communist societies, has been formally submitted to the Polish parliament. There has also been progress on the controversial issue of an independent farmers' union.

The party's attitude toward a rural branch of Solidarity has been changing gradually over the last two weeks and political sources report there is now some hope for a compromise. What is more, until the issue is settled, the goverment has agreed to tolerate Rural Solidarity rather than regard it as illegal.