The petite young woman with the ponytail, hoop earrings and little red knapsack holds her fingers in her ears and shudders with each crash of the cannon.

One by one, the line of Civil War-era artillery pieces goes off -- shh-BOOM! -- each one a little closer, and each one a little more jarring. As the shots come near, the woman has both hands covering the sides of her face, and with the final blast, about 30 feet distant, she turns away in pain as if she has just been slapped.

The firing is, of course, make-believe war -- a masquerade attended by perspiring men and women in gaudy period costume. But as Army Spec. Kristina Steinmetz, 23, looks on here during a visit from Walter Reed Army Medical Center, she is having trouble separating the pretend war from the real thing.

The occasion is a sprawling weekend reenactment of the battle of Gettysburg staged across freshly mowed farmland in the fields north of town. Steinmetz, who is recovering from combat stress at Walter Reed, had come to the reenactment with two wounded comrades on an outing hosted by a soldiers support agency called Operation Second Chance Inc.

Steinmetz, of Phillipsburg, N.J., Cpl. Michael Oreskovic, 23, of Eugene, Ore., and Pfc. Harold Peckenpaugh, 19, of Attica, N.Y., had been eager to make the trip. The three are close friends, and it had been their idea: a three-day weekend away from the hospital. Peckenpaugh had been a reenactor before entering the Army, and his old Civil War outfit would be in the battle. Steinmetz and Oreskovic, a military history buff, had never been to Gettysburg.

But Friday morning, as they were driven to the make-believe war by Operation Second Chance founder Cindy McGrew, each of the young soldiers bore the scars of the real one that is underway in Iraq.

Steinmetz, who looks much younger than her years, had been a convoy truck driver -- one of the most harrowing assignments in Iraq. She told of convoys being attacked daily by roadside bombs, of never knowing what might blow up -- an animal carcass, a pile of garbage -- and of never knowing who in the convoy would survive and who wouldn't. Peace of mind came only at night, she said, under the stars.

Partway through her tour in Tikrit, she began blacking out without warning and developed heart problems. She was taken to Walter Reed, where, she said, she was treated for syncope, a temporary loss of consciousness that can be stress-related, and for post-traumatic stress disorder, from which she has substantially recovered.

Peckenpaugh, a rangy Humvee gunner who wears his Purple Heart pinned to the bill of his blue baseball cap, has a long pink scar down the right side of his neck. On Dec. 4, near Ramadi, he was at his gun when an improvised bomb went off, sending shrapnel into his neck, breaking his jaw and slicing his carotid artery. He lost so much blood that he suffered a stroke and, for a time, was partially paralyzed.

Oreskovic was a scout with an Army cavalry unit. He had spent months on hazardous house searches, "hunter-killer" missions and recons. "It was fun," he said. "I enjoyed it." He had been wounded once by a car bomb, on Oct. 5, and six days later he was hit again, just a week before he was scheduled to come home.

This time it was a huge device, made of mortars and artillery rounds, in a truck full of fruit that blew up near his Stryker vehicle in Mosul. He was exposed from the waist up, manning a grenade launcher in the turret.

"I saw a blue flash, " he recalled. "Turned to red. Got real hot." His squad leader, in the vehicle in front of him, was killed. And the blast tore off Oreskovic's left arm at the elbow. "There was nothing left of it," he said.

He arrived a few days later at Walter Reed, where for the first few months of his recovery he couldn't watch TV or movies about war, and certain sounds made him jumpy and emotional. Gradually, he got over that, and this weekend -- his interest in history piqued -- he did not expect trouble at the reenactment. "I can separate myself from it," he said.

The four arrived at a campground about 11 a.m. Friday, unloaded their gear at the cabin where they planned to stay and headed for the battlefield, where the reenactment continued yesterday and is scheduled to conclude today.

It was the 142nd anniversary of the battle, where thousands perished over July 1, 2 and 3, 1863.

At first glance, the modern-day soldiers looked like anyone in the crowd of onlookers who came to watch the battles and browse under the tents where merchants sold reproductions of 1860s-era clothing and firearms.

Oreskovic's artificial left arm was barely noticeable, protruding from his long-sleeved shirt, though he did fumble a bit getting money from his wallet using only his right hand. Steinmetz and Peckenpaugh each bought cap guns, which they fired at each other playfully. And when Peckenpaugh purchased a reproduction 1858 Army revolver, the clerk asked, "How old are you?" He showed his Army ID card.

But there was a seriousness about the trio as they strolled anonymously among people wearing "Support Our Troops" T-shirts or clad as soldiers from a bygone era. When Steinmetz emerged from one merchant's tent with a feathery blue dream catcher, she muttered to Peckenpaugh, "I need something to take the damn nightmares away."

As the day wore on, the weather grew more sultry. Oreskovic and Peckenpaugh dressed up temporarily in period garb provided by Peckenpaugh's reenactor friends. All three drank bottled water and ate ice cream cones to stay cool.

But by mid-afternoon, the heat and the artillery fire had become too much for Steinmetz. Her hands trembled as she clutched her small digital camera. McGrew held her tightly around the waist during the demonstration.

"It was a little hard," Steinmetz said afterward. "Just flashback memories. You just start thinking. . . . The jump is always going to be there. But just visions, you know."

That evening, as distant bugles sounded and drumfire again echoed among the fields here, she packed her things, caught a ride back to the hospital and left Gettysburg, with an old-fashioned band playing in the town square.

Confederate reenactors set off their artillery at Gettysburg. The reenactment of the decisive three-day battle ends today.Iraq war veterans Michael Oreskovic of Eugene, Ore., left, and Harold Peckenpaugh of Attica, N.Y., dress in Confederate uniforms. Peckenpaugh was a reenactor before he joined the Army.Iraq war veteran Kristina Steinmetz is comforted at Gettysburg by Cindy McGrew, founder of a support group for wounded soldiers.Harold Peckenpaugh carries Iraq battle scars into the reenactment.