The column of armored trucks jumped the curb, cut across a dirt-and-gravel soccer field and made its way north into the maze of narrow streets.

A full moon cast shadows across Sadr City, the insurgent-controlled Baghdad slum. Headlights turned off for stealth, the vehicles crossed into a pitch-dark lot surrounded by abandoned buildings. The lot was filled with reeking garbage and clusters of glaring men.

"Man, I don't like driving across this field," muttered Anthony Stewart, 31, a platoon sergeant from Sumter, S.C., speaking softly, glancing uneasily from side to side. "Yeah," replied the driver, Sgt. Nick Varney, 23, of Ridgecrest, Calif. "It's an easy place to get ambushed."

This Humvee crew -- Stewart, Varney and Salakchay Monivong, 21, a Laotian immigrant to the States who mans a .50-caliber machine gun -- is at the core of the U.S. military's strategy to take back Sadr City, street by fetid street.

Three times a day, four days a week, the men join a four-truck platoon that pushes into this ghetto of 2 million in search of insurgents loyal to a rebellious Shiite cleric, Moqtada Sadr. When the soldiers find the insurgents -- or the insurgents find them -- the soldiers' task is to kill them.

The mission, as viewed by a Washington Post reporter who rode along on four Humvee patrols this week, is at once monotonous, exhausting and, in moments, terrifying. This is the war as it is being fought all across Iraq: American soldiers venturing out of their bases into dangerous streets, confronting myriad unseen risks. They face improvised bombs secreted under the pavement and in unmarked vehicles, mortars and rockets fired by the hundreds, teams of insurgents using light machine guns and rocket-propelled grenades. This week brought a spasm of new violence that raised the death toll of American personnel in Iraq to 1,060.

The soldiers ride for hours to the almost-continuous thump of mortar rounds being fired in the distance, but sometimes go days without seeing the enemy. Between patrols, they return to a spartan base near a blue, onion-shaped monument to the Iran-Iraq war to catch a few hours' sleep. Many doze on the hoods of their Humvees. The soldiers are so accustomed to the sound of mortars that they frequently sleep through them.

As of this week, platoons from the 2nd Battalion, 8th Cavalry Regiment of the 1st Cavalry Division had conducted nearly 3,000 patrols into Sadr City since April, according to the battalion command.

The strategy here is similar to that playing out in other restive areas across Iraq where U.S. forces hope to purge the insurgency and initiate reconstruction projects to win over the populace. Those cities include Samarra, where U.S. forces launched an offensive early Friday to drive out Sunni Muslim insurgents who had taken over the city.

"It's kind of ironic, when you think that the Garden of Eden was supposedly somewhere between the Tigris and the Euphrates," said Varney, steering his Humvee up a Baghdad road the military calls Route Pluto.

The day before, a remote-controlled bomb filled with steel ball bearings exploded about 25 feet from Varney's truck. It instantly killed four Iraqi National Guard soldiers riding in a pickup truck directly in front of him and splattered the armored skin of his beige Humvee with ball bearings.

At the thud of another mortar launch, Varney turned toward Monivong, whose head and upper torso stuck out of the gunner's hatch.

"Hey, Moni, look for mortar signals, like smoke, okay?" said Varney.

"Awright," said Monivong.

"You got a grenade, don't you?" said Varney.

"What?" said Monivong, unable to hear above the drone of the engine.

"Never mind," said Varney. "I got one."

3 Paths to Signing Up

How the three men arrived at the center of the most protracted and deadly American conflict since Vietnam opens a window on the all-volunteer army, which draws hundreds of thousands of young men and women attracted by a mixture of idealism, patriotism and opportunity.

After getting out of high school, Stewart worked at a Sumter furniture plant for $6 an hour. One afternoon in 1994, he recalled, he argued with his girlfriend, got in his car and drove aimlessly around the city until, finally, he arrived at a shopping mall.

Across the street was an Army recruiting center. In high school, when Stewart had been approached by a recruiter, he responded, "Get serious." But now, unhappy and struggling to pay his rent, he signed up on the spot.

"The rest is military history," he said. Today, he is married with four children. Ten years and several postings later, he said he still views his dangerous assignment as no more than a job.

"To me, that's all it is," he said. "I got kids to feed."

Varney grew up in Ridgecrest, a small town in the Mojave Desert. Upon graduating from high school, he worked at a golf course for the summer and snowboarded during the winter. Feeling aimless, he decided to attend a community college in Powell, Wyo., where he could snowboard and study communications. He lasted less than a semester.

"School was always pretty easy to me," said Varney, "but I spent most of my time on girls and partying."

After dropping out, he moved to Laramie to live with his sister Melissa. He had already accepted a job as a night janitor when he was watching television on his sister's couch one night and saw footage from the bombing of the USS Cole.

Varney went to talk with a recruiter. "I felt like I needed to contribute something," he said. "You go through life, taking all the time, and you don't really give back." He signed up.

Monivong immigrated to St. Angelo, Tex., with his family when he was 9. Approached by a recruiter, he was impressed by one essential fact. The Army would give him $50,000 toward his college tuition if he would sign a contract to serve four years.

He has completed three. He is about to send $5,000 to Texas to help his parents buy a house. A cartoonist who draws the company's bulldog mascot, he plans to enroll at University of Texas-Arlington to study computer science and animation. This week, Varney helped him fill out his application online.

The three are part of the 16-man 2nd Platoon of Bravo Company, 2nd Battalion of the 8th Cavalry Regiment, 1st Cavalry Division. The battalion is based in Fort Hood, Tex., but operates in Iraq out of Camp Cuervo, about six miles southeast of Sadr City. Half the platoon is married; just three are nonsmokers.

Thankful for the Armor

Not even Camp Cuervo is totally safe for them; mortar shells land frequently inside the compound. On Wednesday, soldiers heard a loud thump, followed seconds later by a screaming whistle and then an explosion just outside the camp hospital. The blast, which was believed to be caused by a rocket, shattered the windows of rooms housing the battalion physicians, but caused no injuries.

"Jesus, I was just standing there two minutes ago," an American contractor told a reporter as they ducked behind a wall. About 100 yards away, a plume of smoke and dust rose from a courtyard in front of the hospital.

That same afternoon, a mortar shell landed near a huge white tent that serves as the base dining hall. The men of the 2nd Platoon, on break from patrolling, never moved. "We're used to it," said Sgt. Ben Brown, 27, of Tomball, Tex.

The platoon's operations begin with businesslike efficiency. The men don bulletproof vests and helmets and load up the four Humvees parked outside their barracks with coolers containing water, Gatorade and Red Bull.

At exactly 3 p.m. one day, the platoon leader, Lt. Tye Graham, 23, a West Point graduate from Pecos, Tex., yells, "mount up." The soldiers snub out their cigarettes and climb inside the vehicles.

"I never used to be super-punctual," says Varney, steering and loading a 9mm pistol and a black M-16 assault rifle. "Now even as a civilian I am."

Varney, an amateur guitar player, is white and thin, his manner quiet and laconic. His military fatigues cover a lavish tattoo of dice and guitars and webs that snakes up his right arm. Stewart, who is African American, normally rides in a different Humvee, but on this day has filled the spot of another soldier who is on leave. Stewart seems like a more serious older brother to Varney and Monivong, whose smiling, easygoing manner seems incongruous as he stands behind the huge .50-caliber machine gun.

The vehicles move up and down the maze of Sadr City streets, nearly indistinguishable to an outsider, turning back at a busy intersection that the military calls Route Gold. The area to the south represents about 20 percent of Sadr City and is relatively peaceful. The area to the north of Route Gold is increasingly hostile -- crossing into it in Humvees will almost certainly draw fire.

The convoy takes a wrong turn, and Varney, trying to turn around, backs the Humvee into a concrete wall.

"Can we go a day without hitting something?" says Stewart, exasperated.

Children run toward the convoy; most wave, flash a thumbs up and jump up and down with excitement. Some gather rocks to hurl at the Americans. As the Humvees move up and down the streets, their radio antennas and guns brush against thousands of sagging power lines that are used to pirate electricity into the concrete homes. The antennas cause the lines to jump and occasionally sever them.

Every 25 minutes or so, the vehicles stop inside a courtyard. They park in a loose circle and point their guns at the neighborhood while the soldiers dismount to smoke, chat and regroup.

The conversation turns to the day before, when the roadside bomb exploded next to the convoy. Two of the platoon's four gunners, exposed in their hatches, were injured by the blast: Spec. Clarence Maxwell, who took a piece of shrapnel in his right shoulder, separating it, and Spec. Gregory King, who suffered a concussion.

Without the armored vehicles, many of which have been refitted for more protection, the soldiers agree, casualties in Iraq would be far greater.

Horseplay, Then a Raid

On Wednesday morning, the third day of the mission, the soldiers were told to prepare for an operation that was likely to draw contact with the insurgents. A surge of adrenaline swept through the platoon. At 1:30 p.m., after a shower break, the Humvees traveled from Camp Cuervo to the staging base near the onion-shaped monument.

The wait began. The soldiers milled about in a courtyard, playing chess, smoking and heaping good-natured abuse on each other. Many wore brown T-shirts with their blood types stenciled on the front. Brown said people are always giving him grief because it is written so large. "They're like, "Hey, O-positive.' You know what? Everybody knows I'm O-positive.' "

Two soldiers began to wrestle and Graham, the platoon leader, said sternly: "After the mission!" When the horseplay continued, several voices rang out: "Knock it off!"

Nearby, an M1-A2 Abrams tank backed into a parking space. The exhaust from the massive vehicle lit a small tree on fire. The platoon erupted with laughter, then booed when a soldier doused the flames.

Varney took apart his assault rifle, cleaned it, then reassembled it on the hood of his Humvee.

Around 9 p.m., Graham announced that the platoon would have not one but two missions: the dangerous assault, followed a few hours later by a raid on suspected members of the Mahdi Army, Sadr's militia.

Groans followed. It was clear that no one would sleep.

"We're robots; put that down," a soldier said to a reporter. "We're frigging robots."

Two hours later, the dangerous mission was cancelled. There would be only the raid.

The next morning, the Humvees rumbled back into Sadr City. They blocked off a street and soldiers from several platoons, including the 2nd from Bravo Company, burst into the houses.

In one, soldiers found an AK-47 assault rifle, ammunition and a notebook containing documents that indicated an insurgent had trained in Jordan with the new U.S.-sponsored Iraqi police. They handcuffed, blindfolded and detained a man with a prosthetic left leg.

In another, soldiers detained a half-dozen men who they said appeared in photographs with Mahdi Army insurgents.

The men were brought back to Camp Cuervo and left bound and blindfolded at the entrance to the battalion command post.

The soldiers processed the prisoners, then went off for lunch.

Sgt. Nick Varney, 23, of Ridgecrest, Calif., patrols Sadr City as part of a four-truck platoon. "It's an easy place to get ambushed," he says.Salakchay Monivong, 21, a Laotian immigrant, was drawn into the service by the allure of money for college tuition.