NEAR BAGHDAD, Iraq - Before dawn yesterday, advance parties for the Second Battalion, 11th Marine Regiment's four gun batteries moved to scout what they figured might be the unit's final location of the war. As the convoy rolled through the eastern Baghdad suburbs, the Marines shared a sense of relief that the end of their piece of the war seemed near.

Then, just as the sun came up, the Marines drove into an ambush. "I saw flashes coming from a building on the right," said Lance Corporal Kevin Kurlas, 26, of Columbus, Ohio. "I saw First Sergeant [Terry Jones in the vehicle ahead] getting off rounds, tearing into the wall. Then somebody yelled there was shooting on the left."

The Marine unit had just moved north out of a congested part of the suburbs into an agricultural area, with farms and fields and relatively few buildings. The only ominous sign was the sight of dozens of blown-up Republican Guard tanks and armored personnel carriers along the road within a few miles.

The Marines and a Boston Globe reporter traveling in the armored Humvee with Jones, just ahead of Kurlas and roughly in the middle of the battalion convoy, heard a single rifle shot, and scanned the surroundings for the source of the gunfire.

Then, the reporter noticed muzzle flashes coming from the lower right corner of a window in a squat building about 60 yards away. Several bullets skipped off the road between our vehicle and the next Humvee forward. The reporter pointed out the source of the gunfire for Jones, who was in the turret operating the .50-caliber machine gun.

The 19-year veteran fired at the building with bullets that carry enough force to go through the mud wall, anybody inside, and out the other side. Jones, 39, fired nearly 100 rounds , and no more muzzle flashes came from inside.

Behind the convoy, other minidramas were unfolding. On the left side of the road, two militia members fired AK-47s from behind trees, and on the right more fired from inside the buildings.

The Iraqis had been smart about the ambush, waiting until the heavily armored reconnaissance vehicles at the head of the convoy passed before shooting at the more vulnerable Humvees and 7-ton trucks. Fortunately for the Marines, the Iraqis' aim was less precise than their planning.

One bullet glanced off the Humvee I was riding in; no one was wounded in the American convoy. The Marines, though, opened up with all the firepower they had on the buildings and the trees.

Three vehicles away, Lance Corporal Kiki Coleman, 22, of Cleveland, Miss., said he saw a bullet fly into one window of his Humvee and out the other side.

"It just barely missed taking [the driver's] face off," Coleman said. Sitting in the back seat, Coleman leaned as far back as he could to make a smaller target, and unloaded two magazines of bullets from his M-16 into the buildings on the right.

Kurlas said he shot 400 rounds from his Squad Automatic Weapon, or SAW. Elsewhere, Marines emptied clips of ammunition from their M-16 rifles, dropped the clips, and reloaded.

Corporal Corey Brown, 21, of Milwaukee, riding four vehicles back in an open-backed Humvee, lobbed a colored-smoke grenade into the building as soon as the firing started. When the militiamen answered with AK-47 rounds and green, Russian-made tracer rounds, the convoy recognized enemy fire.

Brown shot another colored-smoke grenade - a different color this time - to mark the target and the Marines opened up on the buildings. Brown fired three high-explosive grenades into the buildings on the right as the convoy passed by.

Afterward, other Marines congratulated him for calmly marking the target.

"I just did what I'm supposed to do," Brown said. "With grenades, you just have to get close, in the general area."

Meanwhile, Marines on the left let loose on the men they saw ducking and firing from behind trees.

"There's part of you that was scared of being killed, and part of you that loved the adrenaline rush," Corporal Mysael Santolaja, 21, of Glendale, Calif., said of the ambush.

He said he fired about a dozen rounds from his truck's M-240 machine gun before it jammed. He dropped it, picked up his M-16, and fired another dozen rounds before it, too, jammed. By the time he cleared the weapon, the fight was over. The whole fight had lasted less than a minute.

"It sucks that somebody had to die, but better him than me," Santolaja said afterward. "I'd do it again."