The soldiers stayed in a crouch while sneaking through the weary scrub pines on this venerable base, training ground for 1 million infantrymen since World War I. The first wave of men ran out of the tree line, flopped down in the ragged grass, fired at the "enemy" and missed.

"Terrible shooting," grumbled the officer standing behind the troopers as few of the man-sized targets down range toppled from the bullets. "But they'll get better," he vowed, gesturing to riflemen in the grass. They have to, if the Army's biggest gamble since Vietnam is going to pay off.

The Army hopes that it can safely trade the punch and staying power of some of its regular divisions, which go to war with armored vehicles and big guns, for the speed and stealth of highly trained riflemen striking from woods, city houses or mountain trails.

Undeterred by the coming federal budget crunch or increasing criticism within its ranks, the Army is moving out smartly on light-infantry divisions in the belief that the most likely war on the horizon is a small one.

The next Low Intensity Conflict -- the new buzz words for such little wars as those in the Falkland Islands, Grenada, Lebanon and Nicaragua -- may be decided by which combatants arrive first rather than with the most, according to light-infantry enthusiasts.

Gen. John W. Wickham Jr., Army chief of staff, is the new program's leading advocate. When he took over the Army in June 1983, Wickham said in an interview, he felt that the president and other top civilian executives needed a wider choice before having to use military force to try keeping a smoldering trouble spot from flaming into a big war.

Following the lead of his predecessor, Gen. E.C. Meyer, another light-infantry backer, Wickham said he told his subordinates that the Army's existing light divisions, notably the 82nd Airborne and 101st Airborne of about 16,000 men each, were too "heavy" for quick response.

They would require about 1,500 flights by Air Force C141 transports to fly them and their gear from the United States to a distant hot spot, he noted.

"That's three weeks of airlift," Wickham lamented. "That's not very reassuring to national command authorities who want to deter hostilities. So the thought was let's see if we can create a small, hard-hitting light force that can deploy within a week . . . " by exploiting modern weaponry that a fast-moving infantry squad can carry on its back.

The light division that has emerged can be flown on about 500 C141 flights.

Today's Army is undergoing a wholesale restructuring and is earmarking billions of dollars to create four active-duty light-infantry divisions without increasing its present size of 781,000 men and women. A reserve light-infantry division comprised of people from the Washington area is being formed at Fort Belvoir, Va.

The plan is to find enough clerks, messengers and other rear-area soldiers to form two new 10,000-man divisions and convert two other heavier divisions to the new role. This will give the Army 18 rather than 16 active-duty divisions.

Partly because the Army's restructuring means money and jobs in the states of lawmakers on committees overseeing the Defense Department budget, Congress has not confronted many of the questions being raised by Army officers.

Defense Secretary Caspar W. Weinberger recently brushed aside objections by former Pentagon manpower chief Lawrence J. Korb, who said this is the wrong time to spend billions on an experiment. Weinberger kept light-division funding in the fiscal 1987 budget going to Congress in February.

Weinberger and Secretary of State George P. Shultz are scheduled to grapple with the murky issue of Low Intensity Conflict at a conference at Fort McNair in Washington on Jan. 14-15. The main challenges raised by professional Army officers are:

*Low Intensity Conflict has become too deadly for the best infantry moving without armor because modern weapons are being exported even to the poorest countries. Fast-firing Soviet helicopter gunships sent to Nicaragua are cited as a case in point.

Although North Vietnamese infantry combated U.S. firepower with the stealth and speed of the infantryman, critics of the light-infantry concept contend that the American people would never tolerate the high number of casualties incurred by the North Vietnamese.

*The light division can only fight for three days before running out of bullets and beans. If rushed to a world trouble spot, it might find itself desperately awaiting replacements and supplies that take weeks to arrive.

An ancillary argument is that the Marines already have assault troops afloat near such trouble spots, together with ships stuffed with supplies to keep them fighting, so why have a similar Army force?

*Robbing support units of men to obtain infantrymen for the light divisions will make the underpinning for fighting units so thin that the Army will not be able to fight as long as it can today, especially in Europe.

Gen. Bernard W. Rogers, supreme allied commander in Europe, in making this argument, warned that he has only 56 percent of the ammunition handlers, mechanics and truck drivers needed to maintain a fight in Europe. While saying light divisions have their place, Rogers said the Army should build them by expanding and obtaining a bigger slice of the total defense budget.

Wickham and his allies offer rebuttals, saying light-infantry units would fight only where the terrain is advantageous and would be kept resupplied and, if necessary, supported with "plugs" of artillery units. They said the Marines cannot cover all of the places where the president might want to send a force and that forming divisions without expanding is forcing efficiency and automation on the Army without cutting muscle or staying power.

Soldiers being trained here to become a new generation of light infantry look much like GIs have always looked in the field: loaded down, weary and exasperated but getting on with the job at hand.

An Army Ranger officer training them said the light infantry live in the field a week at a time rather than go to the barracks every night like ordinary trainees. But he acknowledged that most of their training is fairly standard, just more intense.

Maj. Gen. John W. Foss, commandant of the Infantry School here, is a Vietnam veteran and believer in the light infantry. While conceding that much of the training is basic soldiering, Foss explained what is new about the light-infantry divisions being formed:

"We have very consciously moved away from a firepower situation" in which the unit employing armor, artillery and aircraft "blows its way forward and tends to defend itself in a very static manner, requiring a long time to get there and a large backup in supply, into a lighter force that can do a lot of things and will maneuver against the enemy.

"You have to train light infantrymen more intensively" to exploit battlefield skills and maneuvering to make up for loss of firepower.

"You've got to shoot a helluva lot straighter because you don't have as many weapons; you've got to more a helluva lot faster, and you've got to move through rugged terrain because the terrain is your friend. A lot more night fighting. A lot more things that are hard to do."

"Would you put them in the middle of the desert?" he responded when asked how light infantrymen could survive against armor if sent to Iran or Saudi Arabia to protect oil fields.

"Probably not, but you're going to put them into a seaport or an airfield or some place where they can, in fact, use the terrain -- in this case buildings and built-up areas where they are not going to be as vulnerable if they have to fight."

Positioning a force quickly may keep a fight from breaking out in the first place, light-infantry advocates stressed.

If fighting is under way before a U.S. force could be dispatched and the Americans were going to be opposed on arrival, Foss said, "you certainly wouldn't pick a light division. It would be the Marine Corps or Airborne or somebody else."

Foss said "the idea you could put a light division into some country and then fly away and leave it is dumb as hell. You can't do that. Everybody requires sustainability because you are consuming things.

"The sustainability for a light division, the umbilical cord, doesn't require an awful lot. The sustainability for a heavy force requires a heck of a lot -- ships, airplanes, time. The U.S. Army has deployed contingency forces several times and never run out of ammunition and never run out of food and water," he said.

Pentagon budget officials said the Army will spend billions if it completes its plan to form and equip these light infantry divisions:

*The 6th in Alaska where one cost will be an estimated $600 million to improve Fort Richardson, adjacent to Anchorage, and Fort Wainwright at Fairbanks.

*The 7th at Fort Ord near Monterey, Calif.

*The 10th Mountain Division at Fort Drum near Watertown, N.Y., where a new base is being constructed, with $750 million attributed directly to the light infantry.

*The 25th at Schofield Barracks outside Honolulu.

*The 29th reserve division at Fort Belvoir, called the Blue and Gray Division because members will come from Maryland and Virginia.