At a makeshift Army base here, Gen. Wesley K. Clark sits in the camouflaged cargo hold of a five-ton truck, working out details of what will be an assault on Kosovo by the AH-64A Apache helicopter gunships lined up outside.

As charts about feints and flying formations flash on a screen, Army majors slam down the steel air vents to further secure the Deep Operations Coordination Cell, keeping secret the plan they are fine-tuning with Clark and that is supposed to quickly kill off Yugoslavia's military men and machines in the embattled province of Kosovo.

If Clark had his way, say U.S. and NATO diplomatic and military officials who know him well, after the first three days of bombing he would have swooped into the separatist Serbian province with the attack helicopters -- and more. Given his rein, they say, NATO's supreme commander would have poured destruction onto Serb troops in Kosovo, the entire air defense system, and the businesses and command centers of the Yugoslav and Serb leader, President Slobodan Milosevic, along with those of his family and political allies.

But the war that began over Yugoslavia on March 24 has been circumscribed by political leaders who refused at the start to even plan for ground troops -- and who continue to deny Clark authorization to use the Apaches he is so intent on sending into battle.

No modern war involving the United States has been fought without the political direction, and sometimes micromanagement, of its civilian leaders. In Operation Allied Force, the tension has been amplified 19 times as the NATO alliance -- with its 19 member governments -- fights together for the first time in its 50-year history.

NATO military officials say their political leaders have absorbed only some of the lessons of Vietnam. They accepted the notion that the public would turn against the war if allied pilots and civilians died, the officials say, but they ignored the lesson that incrementalism and micromanagement would give the enemy a chance to rethink and reorganize his strategy and tactics.

Yugoslav forces used the delays smartly. They shut down their air defense system, making it harder to target. They moved equipment and command centers into deep underground bunkers, many built to withstand a nuclear war. In Kosovo, they dispersed into small units, hid in the woods and mined the borders against the possibility of a NATO ground invasion from Albania or Macedonia.

To compensate for NATO restrictions, and the Serbs' reaction to it, NATO commanders have come up with their own work-arounds to develop a campaign they believe is more likely to work -- over time -- if civilian leaders and their publics have enough fortitude and patience.

Against this background, Clark last week granted a reporter access over five days to his headquarters near the Belgian town of Mons and to his staff here and in Italy and Albania, generating an unusually detailed look at how the war is being waged and adjusted at the top.

A Less Conventional Fight

Every day, six B-52s and two B-1s, both long-range bombers with fierce destructive capabilities, rain "dumb" iron bombs down on Kosovo. But instead of wiping out large, fixed targets, the bombers are trying to herd tiny numbers of Yugoslav troops and equipment from under the trees into open or predictable areas where precision-guided missiles from smaller strike fighters can then move in for the kill.

In a more conventional war, soldiers on the ground would be the ones to guide missile- and bomb-carrying warplanes to their targets, using radios or lasers. Or infantry soldiers and artillery attacks would force enemy troops to move in a certain direction where they would be vulnerable to planes waiting overhead.

But because no NATO soldiers are on the ground in Kosovo, weapons experts at Nellis Air Force Base near Las Vegas suggested sending B-1s and B-52s to do the job. Less effective than troop maneuvers, the aerial herding has nonetheless helped to mitigate the most obvious military handicap NATO commanders have to live with, the lack of ground troops.

"I'd like a ground force to pin [the enemy] down, make him predictable, make him move," said a senior NATO officer directly involved in the air war. "The B-52 and B-1 is clearly being used in a fashion it was not designed for."

NATO commanders here, and those at the air operations center in Vicenza, Italy, and the U.S. Army's V Corps headquarters here in Tirana, have come up with other imaginative ways to tweak tactics to their advantage. "None of us wanted to fight this way," said the senior NATO officer. "We've brought everything to bear that we could, and we've used it the best we could."

It is nearly impossible to judge for certain how effective the airstrikes have been; NATO officials have refused to release precise bomb damage assessments. As of last week, they say, NATO strikes had caused moderate to total destruction of 250 targets. Another number had been lightly damaged or undamaged. NATO military officials warn, in any case, that there is no specific correlation between destroying a given target and the larger goal of forcing Milosevic to return autonomy to Kosovo and accept a NATO-run armed force to guard the peace.

Clark is aware of the retired senior military officers and analysts who have criticized the campaign as a misuse of air power that is bound to fail. But he counters that every war is different and that military commanders are always adjusting their strategies once a war begins.

"I would say the air campaign is working," he said. "We've always said there are theoretical limits to an air campaign, and all military analysts have pointed this out. But every operation has to be approached with the unique circumstances in which it's conducted and for its own specific political objectives."

Given the history of previous bombing campaigns, it is remarkable that not a single NATO pilot has died in combat out of nearly 30,000 sorties flown so far. Mistakes such as destruction of the Chinese Embassy in Belgrade and a pair of convoys carrying Kosovo refugees have prompted some public and diplomatic condemnation, but the scale of civilian deaths has been the lowest of any operation of this size or duration.

In large part, this is due to the three restrictions NATO imposed on the air war.

The first was that it could produce few allied casualties, a calculation NATO leaders made to hold public support. But this kept strike pilots flying above 15,000 feet for weeks. It meant they had to be accompanied by large numbers of escort planes carrying defensive weapons against Yugoslavia's persistent air defense network, and that they were held away from areas where antiaircraft missiles were still active. As a result, they could not fly over Kosovo much in the beginning.

NATO also asked for a war with few civilian casualties on the ground, in Kosovo and in the rest of Serbia, the dominant republic in the Yugoslav federation. This demand created the most cumbersome, micromanaged targeting process in history. At the outset, targets were reviewed in all 19 capitals. But now only the countries, mainly the United States and France, that propose that a target be struck and that are deploying the fighters to hit it have authority to review and reject it.

Finally, NATO asked for a war that would be small and short because political leaders expressed confidence that was all it would take to shake Milosevic. When the three-day bombing first envisaged failed to sway him and the attacks were prolonged, Gen. Henry H. Shelton, chairman of the Joint Chiefs of Staff, visited President Clinton at the White House with a briefcase full of targets to pick from each day until air planners could come up with a longer-term plan.

During this transition to a broader, longer campaign, at least one scheduled flight of a couple of F-117A stealth fighters was canceled because they had no targets to strike, according to a senior official.

Forced to Improvise

To comply and still fight a war they might win, commanders came up with some new tactics. To help them find the small numbers of troops that travel together, this week NATO is set to begin using, for the first time, an unmanned aerial surveillance vehicle with a laser mounted in its nose. The reconfigured Predator drone, which is steered by a technician on the ground watching its real-time video relay, will be used to "laze" targets for nearby warplanes.

To streamline the process of finding small, mobile targets in the field, intelligence collectors at the "Wing Tip" planning cell at a U.S. base in Aviano, Italy, have equipped the Airborne Battlefield Command and Control Center, a plane that directs fighters and bombers in the air, with special laptop computers downloaded with the National Intelligence and Mapping Agency's classified area maps. They use "NIMA in a box" to compare targeting coordinates with what they are seeing on the ground and with the NIMA maps.

To help break through long-held service rivalries, Clark set up an Army "joint battle coordination group" within the Combined Air Operations Center in Vicenza, at the foot of Northern Italy's Dolomite range about 60 miles southwest of Aviano. The CAOC is largely an Air Force operation, and the Army presence is meant to help keep a focus on targeting mobile forces, the Army's traditional concentration.

Clark also asked the Army's V Corps in Tirana, the Albanian capital, to use the Army's doctrinal emphasis on mobile ground forces to help find and nominate targets in Kosovo using a wide variety of intelligence, including intercepts, satellite imagery and informers.

And to improve the likelihood that the Apache attack helicopters will make a difference in the war, if they are approved for use, Clark imported to the muddy fields of Tirana some of the most respected Army officers around. The base, called Task Force Hawk, is headed by Lt. Gen. John Walter Hendrix, the V Corps commander based in Germany. Also there is Brig. Gen. Richard A. Cody, who led Task Force Normandy, an Apache unit that fired the first shots of the Persian Gulf War.

Finally, Clark quietly unleashed a couple of AC-130 Spectre gunships, whose cannons and ultrarapid-fire Gatling guns became famous during the Vietnam War for their destructive power against people and vehicles. One Apache pilot who watched a videotape of an AC-130 attack in Kosovo recently described it as the most gruesome footage he had seen, with 30 soldiers mowed down by a rain of bullets.

Restrictions on pilots have been somewhat loosened since the war began, but there is still some frustration among airmen and others. For example, they are not allowed to loiter in the target area for long. "Normally you don't have to make four phone calls to make a drop," one frustrated forward air controller, "Duke," said in an interview at the Aviano Air Base.

If forward air controllers -- mainly F-16s and A-10 Warthogs -- that direct fighters to a target cannot find it within the 15 minutes or so they are allowed to loiter, then Vicenza sends the entire strike package to a predetermined fixed target or assembly area. If there is no way to get a clear strike against the second set of targets, Vicenza controllers send the planes on to another target outside Kosovo.

"That's the reason we're standing here now, because we have to be extra careful, too careful in my view," said Duke, who under interview restrictions could only be identified by his nickname. "Right now, it's particularly time-consuming and very difficult and very frustrating, in my mind."

One Conflict, Two Views

There are competing versions at top levels about how the air war has been fought.

One version, expressed by a number of senior airmen and intelligence officers, goes like this: When the White House and NATO realized their initial three nights' strikes would not be enough, Clark and his commanders developed a "leadership strategy" and soon won approval from NATO's political leaders.

The strategy focused warplanes on homes, businesses, command facilities and other places they believed were held in close regard by Milosevic and his inner circle. Yugoslav Army and special police headquarters, bridges in Novi Sad, electrical grids and other targets used by civilians in northern Serbia also were struck to bring pressure on the population.

But just as this new strategy was being executed, the horror of mass expulsions from Kosovo gripped the public's imagination -- and led political leaders to urge that something be done to stop it. "The pressure became intense to do something in Kosovo, although there's not an airman I know who thought we could stop the ethnic cleansing from the air," said one senior official.

Clark responded, said one senior official, by "cramming everything we could" against the forces in Kosovo, the senior official said. But by then it was almost too late. Hundreds of thousands of refugees were fleeing and thousands of men were believed dead or kidnapped. And the high-flying aircraft, still limited by Yugoslav antiaircraft missiles, could not find and destroy the small police units most heavily involved.

The concentration on Kosovo, which lasted several weeks, made Belgrade and the rest of the country a relative sanctuary. Yugoslav MiGs began flying again. Life continued in the cities. Adm. James O. Ellis, the Naples-based commander of the NATO task force in charge of Operation Allied Force, and Lt. Gen. Michael C. Short, the Air Force campaign commander, urged Clark to allow them to return to the fixed targets that the Air Force believes it is more effective at hitting, officials said.

In the last month, these officials conclude, the war has become three: one against Belgrade, one against forces in Kosovo and one against the rest of the country.

Clark offers a different version of the war. He says warplanes have flown against all three target areas ever since the war evolved into a longer campaign. Field forces were always a priority, but the air defense system, and then a long bout of bad weather, kept planes from an all-out push against the Serbs in Kosovo carrying out killings and expulsions.

"Over a period of time, we steadily enhanced our ability to attack the forces in the field. They have been the first priority," said Clark. "It's the most direct means of stopping the ethnic cleansing and it's the most direct means of addressing the humanitarian tragedy which precipitated the intervention."

Whatever the case, one result of the delay in attacking troops was that Yugoslav Army and special police in Kosovo had time to hide themselves and their equipment within the civilian population, where they remain hard to strike without the likelihood of also killing civilians.

Milosevic's military advisers understood early on, too, that aversion to allied pilot casualties was another weak link in alliance cohesion. When, before the war, Clark visited Belgrade, one of the colonels on his command staff got a mischievous lecture from his Serb counterpart.

"Eighteen," the Serb smiled. The magic number.

Eighteen Army soldiers perished in a botched operation in Somalia in 1993, leading Clinton to pull out U.S. forces. The public reaction has framed Pentagon, White House and congressional views of foreign operations ever since.

CAPTION: Gen. Wesley K. Clark, supreme allied commander in Europe, is greeted by Italian military officers as he arrives at Istrana air base yesterday.

CAPTION: A U.S. soldier polishes the windshield of a weapon Gen. Wesley Clark very much wants to use -- an AH-64A Apache helicopter -- at Rinas air base in Tirana, Albania.

CAPTION: Gen. Clark has used the AC-130 Spectre gunship, whose cannons and ultrarapid-fire Gatling guns became famous during the Vietnam War for their destructive power against people and vehicles.

CAPTION: Members of two U.S. B-52 bomber crews meet reporters after returning to Royal Air Force Base in Fairford, England, from first bombing mission in Yugoslavia March 24. At right, a dog passes wreckage of NATO surveillance drone shot down over village of Gornja Vapa May 17.