The Iraqi known as "The Source" slipped the borrowed U.S. military fatigues over his clothes in the back of the armored personnel carrier. He donned a black ski mask that covered everything but his eyes.

He stepped out of the back of the vehicle and addressed the interpreter who would in turn address the company commander who would lead the search for terrorists this day.

"The village. He wants you to arrest all the men in the village," the interpreter told Army Capt. Eric Beaty, commander of Company C, 5th Battalion, 20th Infantry Regiment.

"They're all bad?" Beaty asked.

The interpreter consulted The Source. "Yes, all bad," he said.

"Well, what we'll do is we'll put you up on the top of the Stryker, and you can tell us where to go left or go right, okay?" Beaty said.

A half-dozen Strykers, 21-ton armored vehicles, then rumbled up the road in search of the shadowy enemy that has made much of Iraq -- including this remote agricultural city near the Syrian border -- a dangerous place for U.S. forces.

The six hours that followed revealed much about the challenges faced by U.S. soldiers who are trying to find the men who are trying to kill them.

U.S. forces have controlled Tall Afar since Sunday, after battles last week that killed an estimated 104 Iraqis and displaced 50,000 to 100,000 residents. On Tuesday, soldiers reopened the city to those who had fled. They searched for insurgents among all military-age males who entered, and in sweeps like the one recommended by The Source.

The day began about 11 a.m. at Checkpoint 3 along an asphalt road the military refers to as Route Santa Fe.

Beaty positioned The Source in a Stryker at one of the two rear hatches normally used by machine gunners. His torso and hooded face peeked out of the vehicle as he led the U.S. troops to the village of Tolelhar, on the city's western outskirts.

Seated inside were Pfc. Mario Rutigliano, 19, of Clifton, N.J.; Pfc. Clyde Gean, 23, of Wilmington, N.C.; and Spec. Jared Cate, 20, of Concord, N.H. Along with the rest of the Stryker Brigade Combat Team here, the three have been attacked for months with grenades, roadside bombs, mortars and rocket-propelled grenades.

One of the insurgents' favorite weapons in Tall Afar are RKG-3 hand grenades. The weapons look like coffee cans on sticks and, when flung by insurgents, float toward the target on tiny parachutes, then explode in midair, sending the force of the blast straight down.

"We need to get some music in here," Rutigliano said as the Stryker rolled toward the village.

"Yeah, we do," Cate agreed.

"You lose your mind if you take this stuff too seriously," Rutigliano said.

Rutigliano said he thought the Stryker Brigade had defeated local insurgents, but he predicted they'd be back. "It doesn't matter how many we kill, they'll always keep coming back," he said. "They've all got cousins, brothers. They have an endless supply."

The Stryker stopped in a parched field in Tolelhar. The rear ramp dropped and the soldiers bolted from the vehicle into the blinding afternoon, crouching and sweeping their black M-4 assault rifles across the barren landscape.

The men fanned out and headed for buildings on the other side of the field. A half-dozen soldiers punched through the door of a two-room mud house. Nineteen women and children huddled together in the shade of the courtyard while the soldiers searched for weapons.

Two soldiers came to a large cabinet containing scattered clothes, small teacups, a small Winnie the Pooh doll and a large stack of blankets. The men poked their guns into the blankets on the top shelf and they began to fall. The soldiers scoured the jumble, then left.

Outside the house, other soldiers had seven men lined up facing the mud wall surrounding the house. Two of the detainees massaged prayer beads as the soldiers fitted them with plastic flexible handcuffs and blindfolds. Some wore trousers, others white gowns.

"You have the right to remain silent," one soldier told an uncomprehending detainee in English. "Anything you say will result in a punch in the face."

Most of the detainees appeared to be in their twenties or thirties; one appeared to be at least 70. The soldiers photographed the detainees' identification documents and then the detainees' faces. An interpreter, whom the soldiers called "Terp," wrote down the names on the back of a piece of cardboard torn from a pack of mixed fruit. The names were then compared with a "Black List" -- a computer printout of suspected terrorists.

"Bad guys, bad guys," said one soldier, watching the detainees as they were processed.

"Or maybe just some guys without a home," Beaty said.

The detainees, now numbering 10, were marched single file across the field. Soldiers from five other Strykers had rounded up 83 other men. They were seated on baked earth coated with straw, their hands behind their backs.

One man gave his name as Mustafa Abdul Rahman, 55. He said he was from Tall Afar and had left to escape the fighting.

"They said on the loudspeaker for us to leave the city," he said through an interpreter. During the fighting last week, the Tall Afar police chief had asked residents to leave for their safety.

The man sitting next to him said he had also fled the violence. "We escaped because we were scared," he said. "We came here."

As the men sat, some with their heads tipping forward, others looking around, a soldier yelled, "Get The Source."

The Source, still wearing the borrowed uniform and black ski mask, came forward. He was asked to point out the terrorists in the group. He walked down the rows of detainees, putting his hand on the head of one man here, another there. As he did, a soldier would pick up the fingered detainee and separate him from the group.

"All of the village, they are terrorists," The Source told two journalists after he finished.

Asked how he knew, he said: "I have one guy here, and he passed along the information to me."

Asked how he could be sure, he said: "Yes, they are terrorists. They all have the long beard. They had the beard, but some of them they shaved."

The Source declined to give his name. He then asked: "Is the commander going to pay me any money? If you are an informant, they are supposed to give you money."

The detainees whom The Source had patted on the head were loaded into the Strykers, flex-cuffed and blindfolded. By the end of Tuesday, 49 men were in custody, said Army Capt. Nathan Terra. "This was the most we've ever had, by far," he said. The detainees were so numerous that the soldiers ran out of flex cuffs and blindfolds.

U.S. military officials said the detainees would be held at a detention center inside Forward Operating Base Sykes, outside Tall Afar. Most would be held no more than 48 hours for interrogation, they said, then released.