President Carter's secret war to convert NATO from a dangerous illusion to a coalition capable of fighting the Warsaw Pact has barely started, but more than any other Carter foreign policy it signals the West's loss of strategicc nuclear supremacy and the decline of detente.

Indeed, Carter's unannounced decision to restore former Ambassador Robert Komer to a major role in rehabilitating the North Atlantic Treaty Organization's battlefield capabilities tells much about his inner concern. Komer, in charge of the pacification program at the peak of the Vietnam was and then briefly the American ambassador to Turkey, carries some cold-war baggage that might unfairly have been used against him.

Instead, Komer is now full-time NATO "consultant" in the Pentagon, working closely as Secretary of Defense harold Brown's agent with Gen. Alexander Haig, the NATO commader, and NATO, Henry Owen, now the President's part-time consultant and a former State Department policy-planning chief.

The President was explicitly warned before the NATO summit meeting in London last May that the Warwaw Pact buildup (immense since the 1968 Soviet invasion of Czechoslovakia) has created a NATO weakness even more dangerous to the West than the Soviet strategic buildup.

The fact that this warning came directly from Harold Brown it clear urgency. brown's advice to the President: NATO must quickly - and for the first time ever - be prepared to wage defensive warfare against a possible invasion of Western Europe by Soviet-led Communist forces within a warning time of 48 to 72 hours.

Even before Brown's warning to Carter, he was trying to convince U.S. partners in NATO of their vulnerability to suprise Soviet conventional attack in Central Europe. Hiring Komer was one of these steps. persuading Carter to retain haig as NATO commander was another.

But the real test of the Carter-Brown policy is whether it can surmount Western Europe inertia. That means persuading members to bring their NATO forces up to strength - particularly the Dutch - and persuading all NATO members, including the United States, to adopt interchangeable weapons and ammunition.

The compulsion that for the first time is beginning to drive NATO toward these overdue goals is fear - fear growing out the loss of U.S. strategic superiority (which has ruled out automatic nuclear retaliation in a Soviet attack) and fear that Moscow is approaching a crisis over who will secceed Leonid Brezhnev, further endangering detente.

The Fear seems to be working. One European member has finally agreed to double its forces in the central German front area, meeting the assigned level frot he first time. Strengthening the front against surprise attack was the major recommendation early this year in a widely studied report by Sen. Sam Nunn of Georgia, a respected Democratic defense expert.

Another small NATO member has finally agreed to amajor increase in its antitank guns at considerable expense. Neither of these decisions has yet been announced.

Helping to make these changes possible is a radical political decision taken by the Carter administration at the strong urging of Haig, Owen and Komer. Lobby for essetntial changes in force structure and weapons compatibility at the field-commanders level, not the political level. It is a Haig credo that vital changes must first be agreed to by field commanders, then be sold to the politicians.

Perhaps more important are tentative decisions looking toward interchangeability of weapons and ammunition. For example, the three major NATO air forces - U.S., BRitish and carrying three separate missile systems, each of which is now limited to its parent air force. Agreement has been reached for common use of the next generation of antitank missiles; today eight different missiles are used by differing NATO forces against tanks, a ludicrous incompatibility.

Major tests to come involve compatibility by the U.S. with the European 120-mm tank gun. But the U.S. army has now agreed - for the first time - to study possible adoption by West Germany, Britain and Italy - pointing to a significant breakthroygh in Jimmy Carter's secret war to make NATO take itself seriously for the first time.