Ever since President Reagan went to Omaha Beach last year to commemorate the 40th anniversary of D-Day, we have been engaged in an eerie historical reenactment, 11/2 generations removed, of the march of Allied armies across Europe. Last year it was Normandy. This week, the liberation of Auschwitz. Soon other milestones: the crossing of the Rhine, Hitler's death and finally the surrender of Germany and V-E Day.

Why the obsessive need to mark every painful station of the cross?

In part it has to do with the magnitude of the event: a war that created our world, the "postwar" world, de- Nazified, bipolar and nuclear. In part it has to do with the nature of the interval that separates us from the event. Why, after all, the great celebrations now, and not in 1975 or '65 or '95? Forty years, the Biblical span, has a peculiar hold on the Western imagination. It is the ellipsis, the wait and the wandering, between deliverance and redemption. Now is about the time we should be coming to the Promised Land. Perhaps because we can catch no sight of it, we look back so anxiously and nostalgically to the exodus.

Still, if satisfying anxiety and nostalgia were the only reason, month-by- month observances would indeed be excessive. There is a deeper reason for remembering the war. It has to do with pedagogy.

Consider two items. Last Friday SS Maj. Walter Reder, who led the 1944 reprisal murder of 1,830 Italian civilians, returned home from prison in Italy. At the airport to greet him was Austria's minister of defense.

A few days earlier, the West German chancellor agreed to address a rally of German exiles who dream of returning to their homeland in what is now Poland. Their slogan is "Forty years of banishment: Silesia remains our future in a Europe of free peoples." This was toned down from the original "Silesia remains ours." Either way, it is in poor taste. In the shadow of V-E Day, it defiantly echoes Hitler's idea ("ein Volk, ein Reich, ein Fuhrer") of uniting all Germans in a Greater Germany.

This is not to say, as does Soviet propaganda, that Chancellor Helmut Kohl is a revanchist; only that domestic politics inclines him to gloss over some unpleasant history. Younger Germans may never have learned that history to begin with. They show (the Greens, in particular) a growing tendency to blame the partition of Germany on a conspiracy of the superpowers, especially the United States. They need reminding exactly how American and Soviet armies came to meet in Berlin in the first place. A commemoration of the war Germany started helps.

But what kind of commemoration? That has become something of a diplomatic problem. Last year the Germans were miffed that they were not invited to the celebration of D-Day. They felt that after 40 years of good Western citizenship they deserved a place at Normandy. Moreover, exclusion created domestic problems for the pro-Western Kohl: the anti-NATO opposition was able to argue that the West refuses to accept Germany, and yet makes it bear the burdens and dangers of alliance.

So the idea this time is to include Germany and tone things down. President Reagan said that V-E Day ceremonies are not for "rejoicing (over) victory and recalling the hatred that went on at the time." Accordingly: no concentration camps on Reagan's V-E Day itinerary. "The president thinks we should try to put this behind us," said one administration official. The idea is to underscore "reconciliation."

No doubt the sanitized ceremonies will do something to secure the political fortunes of our friends in West Germany. However, tact has its price. In this case it is truth.

World War II did have a happy ending in which a remnant of Germany was able to lead it back to civilized life. The point of the war, however, was not rehabilitating Germany, but saving the world from it. To emphasize the first, and suppress the second, is not only to reverse cause and effect, but to distort the meaning of the war.

What is at stake is not just historical, but moral truth. This was the most just of wars against the most radical of evils. The reason for recalling that is not to punish Kohl and modern Germany for the sins of 40 years ago, but to teach a new generation exactly what the fight from Omaha Beach to Berlin was for, and against.

The president is a gracious winner. He doesn't like to belabor victories. But this is not a budget battle with Congress, or a win in the Electoral College. This is World War II. Nearly half a million Americans and millions of others died for it. Can we not discreetly ask our German friends to sit this one out? There will be time enough to celebrate their remarkable moral rebirth. That came after V-E Day 1945.