In the hills above this ancient fortress-city on the Rhine, Leopard tanks and Marder armored combat vehicles of the 14th Panzer brigade clank noisily through village streets and then move quietly into the fields and woods of central West Germany.

These two modern weapons of war are probably the best of their kind in any arsenal in the world.

The West Germans have thousands of both in an army that, in the last decade, has grown to become what many Allied leaders think is the best, most disciplined and well-equipped fighting force in Western Europe.

The nearly 500,000-member highly modernized West German armed force in an important factor often overlooked in the debate over whether the strength of the Warsaw Pact forces has reached a point at which NATO is vulnerable to a land attack from the East. It is a debate that has reverberated in Washington, at NATO headquarters in Brussels and in the media of both continents.

Europeans, however, and many Americans and Allied specialists abroad, tend not to overlook the West Germans.

While there is concern throughout Western Europe about growing Soviet military strength, there is less alarm here than that reflected by a barrage of recently released statements in the United States by Sens. Sam Nunn (D-Ga.) and Dewey F. Bartlett (R-Okla.) and retired Army Lt. Gen. James F. Hollingsworth that NATO is in disarray while the Soviets have grown so powerful they can launch a devastating attack on Western Europe virtually from "a standing start."

British Adm. Sir Peter Hill-Norton, chairman of NATO's military committee in Brussels, calls such a surprise-attack scenario "nonsense."

"My considered opinion is that the Soviets can't do that. NATO is neither asleep, stupid, slow to move nor uninformed," he says. "While the warning time before an attack has shortened, I am absolutely convinced it has not been reduced to zero.

"I have a better feel for these things than someone who came here on a three-week visit," he said, refering to the Nunn-Bartlett team that studied NATO readiness in Europe.

The admiral describes all three men as "goodies."

"They are on our side, trying to make NATO better, and they think the way to do it is to scare the hell out of everybody. I don't. It is counterproductive. They are goodies but their judgement is faulty," he claims.

"I disagree with Nunn, Hollingworth, retired U.S. Air Force Maj. Gen. George Keegan and Belgian Gen. Robert Close," says Hill-Norton, "because they have all taken the worst-case scenario.

"You don't have to match a potential enemy gun for gun. It is a historical fact that an aggressor requires a degree of superiority to be sure of success. That degree is debatable, but 3-to-1 is about right and they don't have that in any element. They have an inferior Navy. They have quantitative but probably not qualitative superiority in the air.

They have superiority on the ground approaching 3-to-1 but it depends on how you count it.

"I believe, and so does [NATO commander in chief] Gen. [Alexander] Haig and Adm. [Issac C.] Kidd [supreme Allied commander of Atlantic forces], that NATO forces today are sufficiently well-equipped and close to the battle front to carry out deterrence.

"Sen. Nunn came here and pressed for answers about how much warning time we have and how much additional strength is needed to make an attack with short warning times less likely.

"Nobody in his senses can answer either question because the scenario the Russians choose will determine warning time. What are their objectives? Will there be political indicators?There will absolutely be military indicators," he says.

"The real question is have we got enough. Yes, we have," Hill-Norton says.

"But if the Soviets continue to spend 11 to 13 per cent of their GNP on defense, and European NATO averages 3.8 per cent, then at some point we shall not have enough.

"The Soviets are not 10 feet tall. We are both 6 feet tall. But they are growing faster."

In a dozen interview with Allied defense and political specialists from several countries, and at NATO headquarters, virtually no one in authority believes that the West could indefinitely hold and then throw back an all-out Warsaw Pact conventional attack on Western Europe without eventually using nuclear weapons.

On the other hand, virtually no one believes that the Soviets could or would launch such an attack, or that the Kremlin would have confidence that it would succeed and gamble that it would not result in a nuclear holo caust.

The biggest worry is not the all out assault. Most worrisome, as one British diplomat explains it, is if a crisis should develop somewhere along the flanks, at the tip of Norway or near Turkey, for example.

NATO must then decide to rush whatever reserves it has to that area or to hold back and keep an eye on the crucial Central European front. If the Soviets, in the midst of a crisis elsewhere, used the occasion to pour troops and equipment into the central region and NATO did not mobilize to match it, some fear that the Soviets then might be tempted by a fast blitzkrieg that could get to the Rhine and split Germany in a matter of days.

If an American President did not react fast enough, the intriguing question is raised as to whether the White House would order a nuclear attack on the Soviets after a Soviet attack had stopped, albeit on the Rhine.

On the other hand, some Allied officers think that if the Soviets precipitated a crisis on the flanks, then the Allies could do the same elsewhere, maybe seizing all East-bloc shipping or other such ideas rarely discussed openly.

Some experienced NATO officials believe the current round of alarming talk in some Washington circles is aimed more at ensuring that the Carter administration and other NATO governments gain approval in their respective parliaments for the next round of weapon procurements so that the balance does not tip in the 1980s. That seems to be what Hill-Norton is saying.

Viewed from Europe, which would be the battlefield for a future war, the East-West balance is a vastly complicated panorama that looks something like this:

According to Western intelligence, the Soviets have added 130,000 men to the central region in the past five years. That pushes the total, including Warsaw Pact allied forces, to 920,000 men.

NATO has about 700,000.

The key, however, is that of the Warsaw Pact total, about 600,000 to 700,000 are Soviet troops, and NATO commanders do not think that is enough for a high-confidence initial attack.

With the possible exception of the six highly regarded East German divisions, few analysts believe the Soviets would trust the inclusion of divisions from other countries in a first wave, the crucial one. Others question whether the Soviets could leave countries such as Czechoslovakia dn Poland without occupying Soviet forces during an offensive operation.

The Soviet divisions are smaller than Allied ones and are rated in the West as probably one-third ready to move on eight hours' notice, one-third on 72-hours' notice, and one-third within about 10 days.

In equivalent terms, Allied specialists estimate that the Soviets could field about 50 divisions relatively fast and NATO about 30.

The Soviets, for a much more massive attack, could field 100 divisions, but that would take several weeks and would allow that much more NATO mobilization.

Against a 50-division attack, top Allied commanders are convinced they would have a minimum of 72 hours' warning and probably more since it would be impossible to conceal preparations for such a massive undertaking. No one believes the West - specifically the West Germans, on whose turf the battle would be fought, and the Americans, with 500,000 troops and dependents in Europe - would not take some action during this time.

It is here that the West Germans are the key. They can mobilize faster than the Americans and leave no doubt that they would.

Says one of West Germany's brightest young generals, 48-year-old Deputy Chief of Staff Wolfgang Von Altenburg: "We feel we can hold long enough to get the political decision" in the West, to get the Moscow-Washington hot line working.

"We can hold them for some days" - he doesn't say how many - "without giving up vital territory or having nuclear weapons overrun or suffering troop lossest hat would make us inoperable. But we are on the edge."

NATO officers are less worried about the number of troops in their armies than about their location - in reserve units at home, or far from the potential front line. Large and competent forces can be added to the inplace front-line troops with reasonable warning time, but many NATO commanders fear that the political leadership, particularly in the United States, might not respond to provocative Soviet moves quickly enough.

One top U.S. official noted that "elected governments don't like to take unpopular acts, and mobilization, unless there is absolutely convincing evidence at hand, would be politically very tough, even in Germany and the U.S.

"Governments don't make points by reacting to things that don't actually happen, and the Soviets could do lots of things piecemeal which might not provoke mobilization. They could have a big military exercise one day, dribble all their submarines out of port over a few other days. It could be hard to convince people that we have the warning time."

The Soviets also have problems. Aside from questions of satellite loyalty in a crunch, Allied specialists point out that the Soviets would be fighting on foreign soil against NATO forces defending their homelands.

Soviet military operations give no indication that their commanders have anywhere near the degree of flexibility and resourcefulness to respond to unexpected situations as do Western commanders. Soviet airmen are not well trained, by U.S. standards, nor are Soviet naval forces as experienced at sea.

But the Soviets have large numbers of men and weapons. They have long had about 2 1/2 times as many tanks and artillery pieces as NATO, though Western tanks in many armies are better. The Soviets are said to be producing some 2,000 new tanks a year, more than double the recently accelerated U.S. rate.

Steady growth of the Soviet navy into a global fleet has long alarmed Western navies. And in the last five years or so, the Soviet air force has been modernized: longer-range planes capable of offensive bombing missions behind NATO lines have replaced mostly short-range, defensive fighters.

The Soviets have added long-range, self-propelled artillery for the first time, chemical warfare equipment and river-crossing equipment. They also have deployed 3,000 helicopter gunships with a roughly 35-mile are directly east from the central Fulda Gap attack area into Germany, an action that has Western intelligence officers puzzled.

The general improvement in Soviet forces is in quality rather than in numbers, which is worrisome to the West. The west traditionally has led qualitatively - and still does, but by a narrower margin.

British, American and West Germans believe the Soviet buildup is intentional, directed from the top, and meant to give the Soviets a political edge in any future confrontation.

"The Russians may not be intending to stage an attack tomorrow," says Von Altenburg, "but they want to be able to put on pressure. They are very careful people, as world history shows, always trying to reduce their risk potential. If they play poker, they want a good hand."

Looking at the Soviet buildup, Von Altenburg says, "You must consider they still remember the shock of 1941" and the Nazi invasion. "And they undoubtedly need troops to pacify their satellite countries, plus they do have global commitments now."

Even allowing for that, he thinks, the Soviets still have 60 to 70 per cent more troops than needed for defense in Central Europe, despite economic problems in the Soviet Union.

The Soviet buildup, however, has not gone unmatched and Western specialists believe the West has already offset a substantial portion of the Soviet efforts.

For example, while the British Royal Air Force has been reduced to a shadow of its old self, its squadrons in Germany in the past two years have been totally replaced by newer French-British Jaguar jets and U.S. Phantoms, with a slight increase in numbers. A new British-German-Italian 155 mm howitzer is coming into service now.

The U.S. Air Force in May will begin bringing additional F-111 fighter-bombers to England and new FF-1515 fighters to Germany. U.S. officers also suggest that a major additional boost to NATO airpower can be expected soon.

The U.S. also is producing the new AWACS aircraft to provide early warning of air attack over a European battelfield. Despite some Soviet efforts in the same field, knowledgeable sources say the Soviet version is in no way comparable.

The 190,000-man U.S. Seventh army in Germany, though short of some supplies given to Israel in the 1973 war, is infinitely better-manned and equipped than it was at the peak of Vietnam. Two new brigades have been added and enlisted men and officers stay here longer.

In addition, thousands of so-called "smart" weapons, guided bombs and antitank missiles, have been added to U.S. stockpiles overseas.

On the way, according to U.S. officers, is a new laser-guided artillery shell that fits 155 mm howitzers, the principal artillery piece in the U.S. arsenal. If it works, the shell will give the howitzer a chance to knock out tanks on the move.

Though most Americans do no realize it, the West Germans provide 50 per cent of the ground forces and 40 per cent of the air forces initially available to meet a Warsaw Pact attack.

The West Germans have 3,700 tanks, half of them the superb Leopards, and the older M-48S are due to be replaced by even better Leopard IIs now coming off the production line.

Close to 4,000 of the Marder armored combat vehicles are in service and thousands of the highly regarded French-German-built "Milan" antitank missiles are being added to British, French and West German forces here, including mounting them on the Marder.

NATO commanders do not really know if this is adequate to cope with the Soviet tank advantage. Von Altenburg, however, does not want more tanks on the West German side of the line. He would prefer armored vehicles carrying antitank missiles and armed infantry to stop Soviet tanks.

Ultimately, it is American strength - specifically the Americans' ability to threaten to use, or actually use, nuclear weapons to stop a Soviet on-slaught - that the Europeans depend on.

Talk by President Carter about eventually ridding both sides of all nuclear weapons does not comfort the Europeans because they think they could not cope with Warsaw Pact nations on a strictly conventional level.

There is another factor, too.

"I don't mean this in a nasty way," says Von Altenburg, "but a war in Europe would produce many flags in American windows for losses, and that would be a tragedy. But a long war would be the end of Germany."

In short, the Europeans - not just the West Germans - want the United States to quickly invoke the threat of using nuclear weapons.

Next: The warring tribes