For many of the soldiers, it was their first real taste of combat. In the 18 days they had spent in Iraq since crossing the border from Kuwait, the enemy had proven reluctant and elusive.

Now, the two sides were at close quarters in a swirling dust storm. It was April 7. Fighters loyal to Iraqi President Saddam Hussein -- a combination of the guerillas known as Saddam's Fedayeen and others -- were dug in within yards of U.S. vehicles. They kept pouring into the surrounding area, determined to turn the U.S. Army's worst nightmare into a reality: urban combat.

Using Soviet-era rocket-propelled grenade antitank weapons to counter the U.S. advantage in armor, the Iraqi fighters, clad mostly in civilian clothes, fired from residential buildings and even a mosque, moved around in civilian vehicles and sent suicide bombers in explosives-laden cars against U.S. M1 Abrams tanks and M2 Bradley Fighting Vehicles.

Close to being overrun, the soldiers of Bravo Company and other 3rd Infantry Division units holding one of three key Baghdad highway junctions fought back with everything they had.

According to U.S. commanders, the battles at the three junctions on that hazy day broke the last significant Iraqi resistance to the U.S. invasion and triggered the collapse of Hussein's 24-year rule two days later.

Looking back on the battles, commanders said they realized that in the irregular Iraqi forces, they faced a more committed enemy than they had seen before, more persistent than the Republican Guard divisions that were supposed to be the most potent in the Iraqi defenses. They also saw signs of a strategy based on the success of Somali militiamen against Army Rangers a decade earlier: cut off the attacking U.S. troops from behind, isolate them on city streets and pour in reinforcements to inflict maximum casualties.

But this time the U.S. troops had armor, and it proved more than a match for the ubiquitous rocket-propelled grenade, the Hussein loyalists' weapon of choice. The supply line held, and the swarming irregulars were beaten back by superior firepower. Months of training for urban combat paid off.

"That was the whole turning point of the war right there," said Maj. Roger Shuck, operations chief of the 3rd Battalion, 15th Regiment, of the division's 2nd Brigade. "This mission is the one that cut the snake in half. Once this happened, everything just started crumbling and falling."

This is the story of the battles of Objectives Moe, Larry and Curly, the highway junctions that U.S. planners, in a lighter moment, named for the Three Stooges.

Two 3rd Battalion soldiers were killed and a dozen wounded seriously enough to require medical evacuation in those April 7 battles. About 30 others were slightly wounded and returned to duty. Staff Sgt. Robert A. Stever, 36, of Pendleton, Ore., and Sgt. 1st Class John W. Marshall, 50, of Los Angeles, were killed by RPG rounds while manning the turrets of their armored vehicles on the way to the cloverleaf at Objective Curly.

The losses among the Hussein loyalists -- a combination of Special Republican Guards, Saddam's Fedayeen militiamen and volunteers from neighboring Syria -- were much heavier. Dozens of their vehicles were destroyed and an estimated 350 to 500 fighters were killed.

"It was a pretty ambitious plan to come in with one brigade and take the whole city," said Col. David Perkins, the 2nd Brigade commander.

Instead of the traditional method of moving in gradually to clear and secure terrain as they went, Perkins took an unorthodox approach. He sent his two tank units -- the 1st and 4th battalions of the 64th Armored Regiment -- racing into the heart of Baghdad to seize key installations, then followed up with mechanized infantry, the 3rd Battalion, to occupy the intersections and secure his supply route.

"I knew that if I could stay that night . . . we would own Baghdad," said Perkins, 44, of Keene, N.H. "That was the key to quickly collapsing the regime."

But with battles raging at the intersections and in the heart of the city, all three battalions were running out of ammunition, and his tanks were low on fuel. He figured he had to get the fuel and ammo in by nightfall, or one or more of his units could get cut off and surrounded.

It fell to the 3rd Battalion under Lt. Col. Stephen Twitty to make sure that did not happen.

"Two battalions had gone through, but [the Hussein loyalists] didn't show their hand," Twitty said. "When we stopped at the intersections, it was now a close fight."

At Objective Moe -- the junction of Highway 8 and the Qadisiyah Expressway -- where the fighting dragged on for 18 hours, every vehicle was hit by at least one rocket-propelled grenade. But only seven U.S. soldiers were wounded, just one of them seriously enough to be evacuated, said Capt. Josh Wright, 29, of Girard, Ill., commander of the 3rd Battalion's Alpha Company. The enemy, by contrast, lost as many as 30 vehicles and 150 to 200 fighters, he estimated.

A few miles to the south, Capt. Dan Hubbard and his tanks rolled into Objective Larry under fire from three directions. Objective Larry was a junction linking Highway 8 and a road that crosses the Tigris River at the Al Jadriyah Bridge. There, the 34-year-old former antiques dealer from Johnson City, Tenn., commander of the 3rd Battalion tank company known as the Raging Bulls, watched an Abrams and two Bradleys take rocket-propelled grenade rounds, with minimal damage.

As he secured the intersection, his own tank was hit five times. In all, seven of his company's 17 vehicles were hit, but all kept going. He figures his gunners destroyed at least 20 Iraqi vehicles.

"As the fighting went on, I realized they had no organization," said Hubbard. "It was like fighting a bunch of different groups that didn't know what each other were doing."

Twitty was also at Objective Larry. From his Bradley, he said, he saw two suicide bombers race up the highway headed north. One was in a white van that was hit by machine gun fire and exploded. The other, in a car, made it to a ramp leading to his position on the overpass -- apparently without seeing a berm across the ramp which Hubbard had built.

"The car ran into the berm and exploded," said Twitty, 39, of Chesnee, S.C. "Had the berm not been there, it probably would have killed myself and my crew and the tank beside us."

At the southernmost interchange, Objective Curly, the battalion initially had the least combat power. It was a motley group: a platoon of Bravo Company's mechanized infantry and Bradleys, the battalion's Tactical Operations Center with its M577 command and control vehicles, a few medical M113 armored personnel carriers, a Scout section in Humvees, a mortar platoon and some maintenance vehicles.

Parked at the cloverleaf, the convoy battled the Hussein loyalists for about two hours before Capt. Ronny Johnson, commander of Bravo Company, drove up with another platoon.

"We were surrounded the whole time we were there," said Johnson, 37, of Dallas.

As his infantrymen cleared a trench of enemy fighters within the cloverleaf and some emerged with their hands up, Johnson feared they could have explosives strapped around their waists.

"Make 'em strip!" he shouted over the radio.

Eventually, 30 surrendered, all but two of them Syrians, according to an Arabic interpreter who questioned them.

At the front of the column, drivers and mechanics fired machine guns at muzzle flashes they saw in buildings 400 yards ahead of them.

But as they did so, more fighters infiltrated through the trenches on the other side of overpass pillars to their right, replacing those who had surrendered earlier.

"We walked right up onto 'em," said Cpl. Mountain Robicheau, 24, of Whitneyville, Maine. "I saw them lying in the trenches . . . their weapons all lined up." He dropped onto his side and tossed in a grenade from a few feet away. As he lay under the bridge, he was slightly wounded in one arm by shrapnel.

With bullets and rocket-propelled grenades continuing to pour in from the buildings up ahead, officers called for "danger-close" artillery fire from Paladin 155mm self-propelled howitzers positioned several miles to their rear.

But one of the rounds fell short, hitting a stone embankment within the cloverleaf and wounding two soldiers. The artillery support was called off.

Among the wounded was Pfc. Christopher Nauman, a 19-year-old infantryman. As he was being carried on a stretcher from the trench line, he held his shotgun across his chest. One of four fallen fighters near a pillar suddenly rose and reached for an AK-47 assault rifle.

"This guy's still alive," Nauman shouted as he raised his shotgun and fired from close range.

The worst was yet to come. After what seemed like a lull, two Special Forces trucks -- civilian Toyota pickups parked under the overpass -- took direct hits and burst into flames.

Seemingly emboldened, the Hussein loyalists poured fire into the cloverleaf. An ammunition truck, part of a resupply convoy, erupted in a series of explosions from an RPG round, its cargo setting off a chain reaction of blasts. Another ammunition truck blew up, followed by a fuel tanker and a Humvee.

The cloverleaf became an inferno of flame and black smoke. Soldiers took cover from the exploding rounds amid shouts to get into the remaining vehicles and leave.

In one of the day's many acts of heroism, Sgt. Andrew Johnson, 31, of Mondamin, Iowa, a member of the resupply convoy, jumped into a fuel tanker that was right next to an exploding ammunition truck, and tried to drive it out of the way. It would not start, he jumped out and the fuel truck exploded.

Command Sgt. Major Robert Gallagher remembers thinking, "Here we go again." The 3rd Battalion's top noncommissioned officer fought in Somalia in 1993 as a special operations soldier and was wounded three times. At the cloverleaf, he was hit again, by shrapnel in the leg.

In both places, said Gallagher, 40, of Toms River, N.J., U.S. soldiers faced persistent irregulars who used buildings as cover, and "the severity of the [gunfire] was the same." In Baghdad, however, "the big difference was that we had armor," he said. "That reduced the amount of casualties we had significantly."

"These guys were not the forces that we had encountered previously," Gallagher said. "They had an agenda. They were trained. And they didn't quit. They just kept reinforcing, and they had fairly effective" gunfire.

"At one point I thought, we just can't get overrun," said Capt. Steve Hommel, the battalion chaplain. "Surrendering to those guys is just not something we can do."

For Hommel, a former combat infantryman, one image keeps coming back: a fighter severely burned over much of his body, lying near three dead comrades and a stack of rocket-propelled grenades.

"I made eye contact," said Hommel, 41, of San Diego. "He was saying to me with hand motions, 'either help me or shoot me,' and pointing to his forehead."

The chaplain helped carry the man on a litter to the medic's aid station, where Capt. Erik Schobitz, 30, an Army doctor from Fairfax, tried to help him. But when the unit pulled out to push farther north after seven hours of fighting, the fighter had to be left at the cloverleaf. Tucked under a blanket, he died there on a gurney.

A soldier fires a 40mm MK19 grenade machine gun from a Humvee during an April 7 battle in Baghdad.A soldier stands over a wounded Syrian fighter in a trench where Saddam Hussein loyalists fought a U.S. advance on a key intersection in southern Baghdad. Two U.S. soldiers were killed in the seven-hour fight for the cloverleaf.A soldier from Bravo Company of the 3rd Infantry Division provides cover for an advance on resisting fighters during a battle April 7 for an intersection on the southern edge of Baghdad.