The United States over the last 25 years has designed, built and deployed to Western Europe more than 10,000 short-range battlefield or tactical nuclear weapons to defend the NATO front from a Soviet and Warsaw Pact attack.

Over all that time, however, the United States has never been able to get agreement from its North Atlantic Treaty Organization allies on exactly how those weapons actually would be used in a wartime situation.

The problem was recently stated with icy simplicity by a military analyst at one of the U.S. government's nuclear weapons laboratories:

"In Germany, the towns are only two kilotons apart."

The average yield in the U.S. tactical weapon stockpile is about four kilotons and many of the weapons are much larger, sources say.

Thus the question has always been how these tactical weapons could be used against an invading Soviet force without turning West Germany and other NATO countries into a nuclear wasteland.

While tactical planners played with that dilemma, nuclear weapons designers focused on the bigger strategic intercontinental missiles. Meantime, tactical weapons designed in the late 1950s and built and deployed to Europe in the 1960s began to show their age.

For example, according to informed sources, a number of today's roughly 7,000 warheads -- such as those for the 20-year-old Honest John missile -- are physically unusable because U.S. troops in Europe no longer have the launchers to fire them.

Another segment of older weapons, particularly tactical bombs, can't be used because they are too powerful or too dirty in their nuclear effects.

Other nuclear devices have always been of questionable value. Atomic demolition munition (ADM) is the classic case. Designed to blow up mountain passes and block oncoming forces, the devices have remained in storage for 20 years because West Germans refused to pre-plant them in their soil along invasion routes. They won't even allow digging holes that could be used for ADMs.

In short, the highly publicized U.S. European stockpile of 7,000 warheads has become more important as a deterrent to prevent war from starting than as an arsenal to use once fighting began.

They are primaily political rather than military weapons.

That is the role, for example, of tactical nukes in Vienna-based negotiations that are attempting to cut down the size of the NATO and Warsaw Pact forces that face each other in Uerope.

The United States has proposed removing 1,000 warheads from Europe if the Soviets remove a tank army.

"There are 2,000 candidates for those 1,000 slots," a weapons expert said during a recent interview.

For the first time in almost 20 years, however, the United States is said to be making a serious effort to analyze the European nuclear force -- a process stimulated in part by the controversy over modernizing tactical weapons by means of neutron warheads.

Planners of stockpile modernization are haunted more by the political fallout than by possible military effects.

Because of the short range, currently deployed tactical weapons inevitably would be exploded on some West European ally's soil, since they would not be used until after an attack began.

No NATO country wants to fact the political reality of that situation.

Even if NATO nukes were dropped in Eastern Europe, the prospect is that the Soviets and their allies would respond by sending their own highyield nuclear missiles into Western Europe.

That possibility is so abhorrent to West Europeans that when NATO exercises call for the allies to use nuclear weapons to repel an attack, the scenario never has the Warsaw Pact responding with its own weapons.

Technically speaking, there are no accepted NATO "fire plans" -- specific weapon-firing orders -- for using most of the roughly 7,000 nuclear artillery shells, ground and air defense missile warheads, tactical bombs and other atomic devices in the NATO stockpile.

There are, however, agreed-upon rules for what weapons should not be used, at least not on West European territory. These "NATO contstraints" -- highly classified orders dating to the early 1960s -- reportedly set a general limit of 10 kilotons as the highest yield that can be exploded on NATO territory, declining to zero in built-up ruban areas. Thus nuclear weapons are barred from use in large sections of Europe.

The constraints reportedly also prohibit use in NATO territory of ground-burst bombs and warheads. Their fireballs would create a radioactive fallout could that could not be controlled on the closely populated continent.

"Never have so many intelligent men spent so much time on a subject, come up with more irrational ideas -- and known it," was the way one former military man summed up the military planning for European tactical nuclear weapons use.

Of course, not everyone talks that frankly or has that point of view.

Gen. Andrew Goodpaster, currently commandant of West Point and NATO commander from 1970 to 1975, spoke during a recent interview of "differences of concept and preference" among the NATO allies on nuclear weapons employment.

But, Goodpaster maintained, there are "realistic" plans for "selective use... accepted up to a degree."

The one thing that the NATO allies all agreed upon, Goodpaster stressed, was the deterrent value of the weapons.

Dwigt D. Eisenhower, first as NATO commander and later as president, "had a clearer recognition of deterrence rather than use" as the prime benefit of tactical nukes, Goodpaster said. "It was Eisenhower's concept that by building up this force it was unlikely we'd have to employ it."

This approach is well illustrated by the 280-millimeter "atomic cannon" that was among the first weapons shipped to West Germany in the mid-1950s.

It was so big it required a driver in the frong and back, much like a hook-and-ladder fire truck. Horror stories about the 280-millimeter depict it rolling off narrow German roads or getting stuck trying to make turns in small villages.

"The Soviets would have had to attack when we had the cannon in the right place to fire at them," a former official said recently, "because we sure as hell could not have driven it to the battlefield."

Though unusable, the atomic cannon set the pattern for the tactical nuclear weapons that followed.

"It was very visible," said a key weapons analyst in ticking of its attributes. "It certainly fired an atomic round; and politically it gave credence to the idea that we had the capability to resort to a nuclear defense."

Almost without planning, those became the common attributes of the various tactical nukes that were built and added to the stockpile.

Practical military application, however, was never a required prerequisite.

The most recent attempt to get an acceptable plan for a new nuclear weapons system began almost five years ago and ended in failure last year.

It was built around the development of neutron artillery shells which were designed to reduce blast damage to areas adjacent to the battlefield.

Presently deployed nuclear shells destroy enemy targets primarily by blast and heat. The nutron versions would depend on radiation, and their area of blast will be much smaller. Thus, it is argued, they will create less collateral physical damage in adjacent areas.

According to informed sources, a proposed U.S. Army operation manual describing how the then-expected neutron artillery shells and missiles would be used was termed "unacceptable" last year by the West German military.

The plan was imple. Circles were drawn around every German town with a population of 1,000 or more. U.S. nuclear planners then devised neutron weapon "packages" of 30 or more shells or missiles that would blanket those areas not covered by circles.

If a Soviet breakthrough occurred and a NATO commander wanted clearance to use neutron weapons, a request would go up through NATO channels to the U.S. President to approve use of one or more of the preplanned area neutron packages.

The German, according to informed sources, refused the manual because it accepted 10,000 civilian casualties with each neutron area package.

"Politically," a neutron proponent said recnetly, "they did not want that coming out in peacetime."

Lack of an accepted plan, however, did not deter President Carter from proceeding with production of the new 8-inch nuclear shell and Lance missile warheads.

The shells were justified on grounds of being better than the shells they would replace. Their range will be longer, they could be converted to more powerful neutron versions, and they will have security devices (which present ones don't have) that disarm them and thus make them less susceptible to terrorist attack.

The new Lance warhead, whether neutron or not, sources said, is needed because the current ones' yields are either too high or too low - too high to comply with constraints on NATO territory use; too low to be effective against Soviet tanks.

Politics also seems to be behind the push for a new medium range missile to be stationed in Europe. Carter recently approved advanced development of warheads for an extended-range Pershing issile and a ground-launched cruise missile, both of which culd reach Soviet territory from West Germany.

By developing two weapons, the United States all but guarantees that one will eventually be produced and deployed.

Next: The competition to build .