THE COMMEMORATION of past military victories always carries a heavy freight of political symbolism for the present and future. When governments organize the celebration, it usually tells you more about today's purposes than yesterday's great events. The decennial observances of the triumphs of World War II have always been a fairly accurate indicator of the condition of the alliances that followed it.

The British and Americans, for example, tried to use the 20th anniversary of D-Day to kindle a recollection of wartime unity in the unsympathetic bosom of Charles de Gaulle, then president of France. De Gaulle was at the height of his power, and full of mistrust toward the Anglo-Americans. The appeal to martial emotion failed. De Gaulle not only boycotted the celebration, but refused to allow any of his Cabinet to attend, with the exception of the minister of veterans' affairs. The Anglo-Americans landed in Normandy without him in 1944, and they could celebrate it without him in 1964. Two years later he pulled the French forces out of the NATO military command.

The 40th anniversary of D-Day, last June, was less divisive among the wartime Allies. But it made another kind of trouble, for they had declined to invite the Germans to attend. The incident has left a residue of irritation in West Germany as a deliberate slight to it as a member of the present alliance.

That's why the Germans are giving careful attention to plans for the anniversary of V-E Day, the end of the war in Europe, next May 8. President Reagan will be in Bonn a few days earlier, with his counterparts from the other leading industrial democracies, for their annual economic summit meeting. That ensures great attention to the place and the occasion. Any commemoration, or lack of it, will become a statement about the current relations among these countries.

To take one basic question: What, precisely, is being commemorated? A victory over fascism and the Nazi Party? Or a victory over the Germans? The first formulation strengthens today's alliance. The second does not. It's worth reflecting that NATO has become one of the wonders of diplomatic history. After 35 years, it is still in working order. To build it took a great deal of faith, and a great deal of magnanimity, among both those who won the war and those who lost it. To become careless of those qualities, and to begin taking them for granted, would be worse than foolish.