The ''Star Wars'' debate in the United States is being followed with a mixture of fascination and concern in French political and military circles. Fascination, since space represents a new dimension for the future; concern, because if a system of preventing a missile attack were discovered, the very foundation of French strategy would collapse.
The French have their force de frappe nuclear strike force. It is small compared to that of the superpowers, but devastating enough to discourage an aggression against their territory. France's policy of independence was built around it.
Were the Soviets to acquire the capacity to stop incoming French nuclear missiles, while preserving their own ability to hit France, the French, of course, would lose both their deterrent and the ability to act independently. They would be left with totally inadequate conventional forces to contain a Warsaw Pact assault.
The ''Star Wars'' doctrine belongs for the time being in the realm of hypothesis. Many US scientists doubt its feasibility. The French seem to be less skeptical, since so much of their own future depends on it.
''We must look beyond the nuclear weapon or we shall soon be left behind,'' President Francois Mitterrand said recently. ''Nuclear technology may become dated, perhaps sooner than we think, in any case, as one of the elements, no longer as the main one, of future strategies, the future being before the end of the century.''
This theme was echoed by Prime Minister Pierre Mauroy: ''Faced with these new challenges, it seems to us that Europeans must mobilize. It would be a mistake to try to defend tomorrow's Europe with yesterday's means and organization.'' President Mitterrand says that a European Community of Space ''may represent the best answer to tomorrow's military realities.''
The uncertain future and realization that France cannot separate its destiny from that of Europe have led to what observers consider the most sweeping revision of French strategic policies since the 1966 decision to leave NATO's integrated command.
In the past, its own nuclear deterrent and political detente in Europe represented the two pillars of France's defense policy. The reality today is that East-West detente had faded while deterrence may at best shield France from an all-out nuclear attack, not from involvement in a conventional war.
The new French strategy assumes that conventional arms have acquired such precision and destructive power that in case of conflict - even assuming, but not granting, the non-use of tactical nuclear weapons - Europe would be devastated.
The issue, therefore, becomes how to deter war in any form. The only practical way is to keep Warsaw Pact forces from crossing the border into West Germany.
The closer ties between West Germany and France represent a reflection of this reality. Clauses of the 1963 Franco-German Friendship Treaty dealing with military cooperation have been activated for the first time, leading to regular consultations between the two governments on a range of military and strategic issues.
The French have undertaken practical steps to reassure the West Germans. One was the replacement of the Pluton tactical nuclear weapons, only capable of reaching a battlefield within West Germany, with the longer-range Hades, capable of reaching enemy forces in East Germany. Another step was creation of a Rapid Intervention Force of 47,000 men that can be mobilized in a matter of hours, and includes in its equipment 150 antitank helicopters.
The Franco-German axis represents a nucleus that both Paris and Bonn hope will eventually extend to the whole of Europe. The French have also taken the lead in reviving the West European Union created after the war to check on West German rearmament. It could represent a means toward a European defense and a lesser technological dependence on the United States.
A number of obstacles stand in the way, however:
* According to French military sources, the Soviets have 9,800 nuclear warheads targeted at Europe. The French, for their part, have 98 nuclear warheads, 80 of which are strategic in the sense that they can reach targets inside the Soviet Union. France's new nuclear submarine Inflexible is being armed with 16 missiles, each containing six warheads with a range of more than 4 ,000 kilometers. American military experts consider the new missiles to be, in certain respects, superior to their US counterparts.
The sole purpose of this deterrent, capable of inflicting 15 million to 20 million losses on the Soviets is to protect the French territory. President Mitterrand has made it clear that France cannot extend a nuclear umbrella to West Germany or any other country.
* What France cannot do, the United States can. Strategists feel that if Washington's determination to use the nuclear weapon in the defense of Europe were only 1 percent, that would be 1 percent too many as far as Moscow is concerned. The smaller European countries, especially, prefer the protection of a power on the other side of the Atlantic to one next door.
* The eventual creation of a European defense community would imply a revision of the Atlantic dimension, deeply modifying NATO and the nature of Europe's ties to the United States.
As West Europe reviews its strategic thinking, the basic issue, it is felt here, is one of political will. If the political will prevails - despite internal differences, Soviet efforts to decouple Europe from the United States, and the waves of neutralism and pacifism periodically sweeping through Europe - Europe can look at an uncertain future with relative confidence.
French politicians and strategists prefer not to think what the alternative might be.