One blistering afternoon in Iraq, while fighting insurgents in the northern Iraq town of Mosul, Sgt. Sinque Swales opened fire with his .50-cal. That was only the second time, he says, that he ever shot an enemy. A human enemy.

"It felt like I was in a big video game. It didn't even faze me, shooting back. It was just natural instinct. Boom! Boom! Boom! Boom!" recalled the fast-talking, barrel-chested 29-year-old from Chesterfield, Va. He was a combat engineer in Iraq for nearly a year.

Like many soldiers in the 276th Engineer Battalion, whose PlayStations and Xboxes crowded the trailers that served as their barracks, he played games during his downtime. "Halo 2," sequel to the best-selling first-person shooter game, was a favorite. So was "Full Spectrum Warrior," a military-themed title developed with help from the Army.

"The insurgents were firing from the other side of the bridge. ... We called in a helicopter for an air strike. ... I couldn't believe I was seeing this. It was like 'Halo.' It didn't even seem real, but it was real."

This is the video-game generation of soldiers. " 'Ctrl+Alt+Del,' " the Army noted in a recent study, "is as basic as 'ABC.' " And computer simulations, as military officials prefer to call them, have transformed how the military fights and how soldiers kill.

"There's been a huge change in the way we prepare for war, and the soldiers we're training now are the children of the digital age who grew up with GameBoys," said retired Rear Adm. Fred Lewis, a 33-year Navy veteran who heads the National Training Systems Association, a trade group that puts on the annual Interservice/Industry Training, Simulation and Education Conference, the military counterpart of the glitzy Electronic Entertainment Expo.
"Live training on the field is still done, of course, (but) using simulations to train them is not only natural, it's necessary."

War is no game, of course. But games, in a big way, have updated war. The weapons Swales uses when he plays "SOCOM3 U.S. Navy SEALS," for example, are virtual replicas of those he used as a soldier in Iraq.

"The technology in games has facilitated a revolution in the art of warfare," said David Bartlett, former chief of operations at the Defense Modeling and Simulation Office, a high-level office within the Defense Department and the focal point for computer-generated training at the Pentagon. "When the time came for him (Swales) to fire his weapon, he was ready to do that. And capable of doing that. His experience leading up to that time, through on-the-ground training and playing 'Halo' and whatever else, enabled him to execute. His situation awareness was up. He knew what he had to do. He had done it before — or something like it up to that point."

In the mid-1990s, Bartlett, an avid gamer himself, created "Marine Doom," the military version of the original "Doom," the granddaddy of first-person shooter games. The simulation was conducted in a lab with six PCs networked together. It served as a precursor for more expensive, highly immersive, state-of-the-art military simulation centers and PC labs. Some, like the Asymmetric Warfare — Virtual Training Technology, largely train soldiers how to coordinate complicated missions. Think of it as a sort of military "EverQuest" that can be played by multiple people in multiple places at the same time. With the Indoor Simulated Marksmanship Trainer, soldiers train to effectively shoot their weapons by holding a rifle that looks like an M-16, except it fires a laser and the target is a giant screen.

Lt. Col. Scott Sutton, director of the technology division at Quantico Marine Base, where the mock-up M-16s are used, said soldiers in this generation "probably feel less inhibited, down in their primal level, pointing their weapons at somebody." That, in effect, "provides a better foundation for us to work with."

No one knows for sure whether Sutton is right. Since at least World War II, studies purporting to explore how readily troops pulled the trigger — S.L.A. Marshall's "Men Against Fire," for example — have aroused controversy and been scored as anecdotal. Collecting data in the swirl of battle is no less formidable a challenge today than in the past. As a result, comparisons to previous generations of soldiers are problematic. Nonetheless, soldiers today are far more knowledgeable about weaponry than their predecessors, Bartlett feels sure, and have "a basic skills set as to how to use them."

Retired Marine Col. Gary Anderson, former chief of staff of the Marine Corps Warfighting Lab, agrees, and takes it a step further: Today's soldiers, having grown up with first-person shooter games long before they joined the military, are the new Spartans.

"America's Army," a free online game with more than 6.5 million registered players, is being used by the U.S. military as a recruiting tool. "Call of Duty," "Medal of Honor" and "SOCOM," to name just three best-selling military-themed titles, are popular with soldiers, in both Iraq and the U.S. A version of "America's Army" will be available on cell phones this summer.

"Remember the days of the old Sparta, when everything they did was towards war?" says Anderson, now a defense consultant. "In many ways, the soldiers of this video-game generation have replicated that."

Still, many PlayStation-playing soldiers aren't as battle-ready as they think. Evan Wright, author of "Generation Kill: Devil Dogs, Iceman, Captain America, and the New Face of American War," a stirring account of young Marines in Iraq, spent six weeks in early 2003 with the 1st Reconnaissance Battalion — nicknamed the "suicide battalion" — which traveled far ahead of the main invasion force. Troops he interviewed were "on more intimate terms with the culture of video games, reality TV shows and Internet porn than with their own families."

But he said: "What I saw was a lot of them discovered levels of innocence that they probably didn't think they had. When they actually shot people, especially innocent people, and were confronted with this, I saw guys break down. The violence in games hadn't prepared them for this."

Sgt. Michael Stinetorf, one of the 1st Recon Marines, used three weapons in Iraq: a heavy .50-caliber machine gun, an M-249 light machine gun, and a suppressed M-4, "which is an M-4 with a silencer," he said.

Before he left for the war, he had played shoot-'em-up games, mostly James Bond titles and "Grand Theft Auto III." Since returning home in September 2004, he can't stand watching his friends play those kind of games, much less play them himself.

"It just doesn't appeal to me anymore," said Stinetorf, now 23 and a freshman at Grossmont College, San Diego, who hopes someday to study medicine. "I found the easiest way to release all the violence, to walk away from it all, is not surround myself with it."

So he says no to violent games, violent movies, violent TV. He declines to talk about how many people he shot while in Iraq.

"That's one thing I don't get into. Even to my closest friends," he said. "It's kind of a way to separate yourself from it."

Unlike Stinetorf, Swales can't get enough of shooter games, especially military-themed ones. He got back from Iraq more than a year ago. A banner that reads "Welcome Home Que" still hangs in his room, in the home he shares with his mom, sister and niece. Nearby, three commendation medals are collecting dust.

Swales, 29, until recently worked two jobs — in Wal-Mart's produce section from midnight to 9 a.m., and at Best Buy, from 3:30 to 10:30 p.m., with a sideline gig installing car stereos. He quit Best Buy a few weeks back. Too much work.

In his spare time, he relives his days as a soldier in front of his TV, playing "SOCOM3 U.S. Navy SEALS."

Swales is sitting in his room, gripping his controller.

"Can you hear the heartbeat?" he asked the visiting reporter. "That's my heart. In the game. When you're trying to get a steady shot, you hear the heart beating. That right there felt like the real thing."

REAL SOLDIERS PLAY MILITARY VIDEO GAMES

Sgt. Sinque Swales joined the National Guard in 1998 "as a way to get my life in track," he says. While deployed in Mosul, Iraq, he mostly hung out with Sgt. Sean Crippen, Spc. Alfred Trevino and Spc. Mike Jones — they were all in the Guard, all in their 20s, all from Virginia. They were dubbed "the minority squad" (Swales and Crippen are black, Trevino is half Mexican-American, Jones is Korean-American). To pass the nights, they watched such classic war movies as "Full Metal Jacket" and "Apocalypse Now."

"Saving Private Ryan" was their favorite.

"That's gonna be us, man, when they first opened the doors on the boat, when they're hitting the beach, just watching guys get mowed down," Swales, the eldest of the group, the big brother type, would joke.

Even more, though, they played military-themed games. "Sometimes we'd be up till 2 or 3 in the morning, and we gotta get up, like, 0900," military-speak for 9 a.m., to head out on foot patrol, recalled Crippen, 23.

"We're doing this stuff for real and we're playing it on our spare time," said Swales, 29. "And yeah, it was ironic. But it was so normal. We didn't think nothing about it."

Swales had a PlayStation2 in the portable trailer he shared with Crippen. They became roommates after their former roommates, Spc. Nick Mason and Spc. David Ruhren, died from a bombing attack. Nearby, Spc. Idrissa Hill, who was rooming with Jones, had an Xbox and a PlayStation 2. Everyone kept busy. Crippen, by far the group's best gamer, got through the last levels of "Call of Duty" and "Full Spectrum Warrior," both military-themed games.

"The very first time I fired my rifle (an M-249 squad automatic weapon, a machine gun), I was scared. I had never shot my gun before at an actual person. But once I pulled the trigger, that was it — I never hesitated," said Crippen, 22. "All I saw was the street where the RPG (rocket-propelled grenade) came from, and I just fired in that direction, maybe 20 rounds at most, and it felt like I was playing 'Ghost Recon' at home," referring to a Tom Clancy game.

"I've always had access to a shooter game. Ever since I could pick up a controller," he said. One of the first games he recalls playing as a kid was "Commando," a shoot-'em-up in which the character Super Joe is dropped into a jungle and tries to fight his way out.

"And over there in Iraq, I think playing those games helped. It kept me on my toes. It taught me what to do and what not to do," said Crippen, now a sophomore studying computer engineering at Virginia State University.

Trevino's weapon was the M-16A4 assault rifle.

"You just try to block it out, see what you need to do, fire what you need to fire. Think to yourself, 'This is a game, just do it, just do it,' " said Trevino, 20, recalling his first shot at a human enemy. He lives in Virginia Beach and works at nearby Bradco Supply. A hard-core gamer like Crippen, he plays "anything that races, anything that shoots."

"Of course, it's not a game. The feel of the actual weapon was more of an adrenaline rush than the feel of the controller," he said. "But you're practically doing the same thing: trying to kill the other person.

"The goal is the same. That's the similarity. The goal is to survive."