Icy winter gusts sweep across the rifle range, slicing into a cluster of white, one-story, cinder-block buildings in the far western edge of the sprawling Marine Corps base here.

The landscape is spartan and alien, a fit setting for an exclusive school that teaches one of the loneliest, deadliest missions the military offers.

Like those who train here, the school's credo is lean and mean: "One Shot, One Kill."

This is the Marine Corps' Scout Sniper Instructor School, a graduate course in bushwhacking for Army, Navy and Marine Corps personnel with a curriculum learned the hard way in Vietnam, Korea and before.

"The bottom line is to kill people," said Capt. Steven L. Walsh, 28, the tall, sinewy officer in charge. "It's a specialty, like flight school. Some guys make it, some guys don't."

The instruction does not emphasize sharpshooting: firing from behind friendly lines. It teaches assassination from ambush over long distances with a high-powered rifle.

"We're the bad guys," said one ex-Vietnam sniper.

The mission requires stealth, patience, marksmanship, field craft, stamina and nerve. Sniper stories from Vietnam are harrowing tales of operating miles inside "Indian country," waiting in a "hide" for a full night, or a night and a day, or even a week for a "target of opportunity," usually an enemy officer.

"I can guarantee you it's very lonely," said E.J. Land, a retired Marine major who also did the job in Vietnam.

A centuries-old tool of warfare, sniping is being refined here as a military option with modern-day applications. Snipers are invaluable for light infantry maneuvering and nighttime defense, and, in the twilight zone of terrorism, the role of snipers is gaining importance, according to military leaders.

The training here is secretive and there is a certain defensiveness among the Marines, who are gung-ho for the program but wary of controversy. The student body is select: Classes of about 20 carefully chosen candidates train for eight weeks in tactics, stalking and land navigation before returning to regular duties.

The weapon of choice is the M40-A1, a bolt-action, single-shot rifle produced by the Marine Corps' armory in one of the cinder-block buildings and not available in your local gun shop.

Marines sew their own "ghillie suits," elaborate camouflage outfits that blend eerily into vegetation, transforming the rifleman into a killer shrub. Making the suit is "part of the passage into the sniper community," said Land.

Do students undergo psychological testing?

"No comment," said Walsh, who was a sniper in Beirut. Sniper methods and deployment also are not open for discussion.

The school was begun in 1976 to offset a tendency to let sniping skills lapse between wars, then scramble to catch up in the heat of hostilities. It is supervised today by Lt. Col. David Willis, 51, commanding officer of Quantico's Weapons Training Battalion and one of a declining breed in the modern Marine Corps: a bona fide, tobacco-chewing, top-seeded character.

A "double distinguished" marksman in rifle and pistol shooting, Willis oversees his domain -- the Marines' marksmanship training and competitive shooting programs, as well as the sniper school -- from an office that is more a marksmanship trophy room, a shrine to the concept that a trained Marine shooter with a single bullet can be a formidable weapons system.

On one wall is a "Sands of Iwo Jima" movie poster featuring John Wayne. Under the colonel's desk, often, is his German shepherd Bruno. Chewing tobacco is stashed in a silver trophy cup, and a large paper bag of roasted peanuts graces the long conference table. Willis' head is shaved.

The gospel according to Willis is a tenacious belief that excellence with a firearm still matters.

"My son [a Marine helicopter pilot] and I got that 'Rambo II' recently to critique it," he said, firing a round of tobacco juice into the wastebasket. "It's horrible. Millions of rounds of ammunition. Helicopters sustain multiple hits and continue to fly. We've got to convince [young Marines] it's not just spraying the area. One well-aimed round is the name of the game."

Automatic weapons are disdained.

"Studies [of automatic fire] show the first round hits the target," he said. "The second round is at 11 o'clock or 1 o'clock, usually 11. The rest marry with the sky. It's wasted ammunition.

"In life, it's adrenaline [that counts]. But in marksmanship, it's total concentration, total control of your body."

The least movement, he said, even a heart beat, "oscillates out your front sight. The same sort of patience goes into sniping."

The school's regimen is demanding, and some do not finish.

"We have a relatively significant attrition rate," Walsh said. "People who either are not psychologically prepared to do it, or emotionally, physically.

"Eventually, they come in here," he added, "and say 'I can't do it.' We don't drop 'em. They leave."

It is a special breed that perseveres, according to several Marine officers, a sort of latter-day frontiersman at heart, self-sufficient and not overwhelmed by doubts about the propriety of the task at hand -- which is not murder, under combat rules, but uncomfortably akin to it.

With a powerful telescope, said Walsh: "We have the capability to watch people die, his head explode or whatever. It's the mark of a true professional to carry out the mission."

"A sniper is the kind of guy who could sit on the porch and whittle a stick all day," said Chief Warrant Officer Charles W. Henderson, whose book, "Marine Sniper," will be published this spring by Stein and Day. "He's at peace with himself."

The consummate Marine sniper in Vietnam -- and the subject of Henderson's book -- was Carlos Hathcock, who helped run the Quantico school in its early stages.

Assigned in Vietnam to "eliminate" a senior North Vietnamese officer, Hathcock took three days and nights to maneuver himself 1,500 yards into position, undetected by nearby patrols, bitten by insects, relieving himself in his trousers and lying frozen until a poisonous bamboo viper he met "head on" elected to slither away.

"That snake's a two-stepper: You get about two steps after it bites you," said Hathcock, now retired and living in Virginia Beach. "I'll never forget it.

"When I made the hit, it was a funny thing: Everybody looked the other way searching for the source of the gunfire ."

There was a depression in the ground nearby, he recalled, and "I just oozed back in there" and escaped.

Hathcock had 93 confirmed kills in Vietnam, according to Land, who oversaw Hathcock's work.

The point of such experiences, said Willis, is that skill and personal fortitude, more than technology, are critical.

"There's a lot of tactics involved," he said. "You just don't send a guy out to get a Medal of Honor posthumously."

In the end, Willis added, "There's one thing we don't know" about a sniper who has another human being in his gunsights: "We don't know if he'll pull the trigger."