U.S. troops advanced through the deserts of southern Iraq in armored convoys Friday, met by surrendering soldiers, and Marines punched through Iraqi resistance blocking the main road to the key city of Basra. Supported by Cobra attack helicopters and howitizers, Marine tanks and armored vehicles rolled through the demilitarized zone between Iraq and Kuwait onto Route 80, which leads to southern Iraq's largest city.

If U.S. forces secure the road, it would speed movement on Basra - 20 miles north of the border. Though the night, the 1st Marine division had been poised in the DMZ, trading mortar fire with Iraqi positions, waiting to break through the sand bergs on the Iraqi side of the zone.

Resistance in the region south of Basra - near the Persian Gulf coast - appeared stiffer than elsewhere along the Iraq border as U.S and British forces opened the ground assault Thursday night, rolling into the desert in several locations.

Further west, some 200 Iraqi soldiers surrendered to the U.S. 15th Marine Expeditionary Unit just over an hour after it crossed the border Friday morning.

One group of 40 Iraqis marched in formation down a two-lane road toward the Americans and gave up. They were told to lie face down on the ground and were searched by the Marines.

At the same time, the Marines cleared bunkers, emerging from one with two Iraqis with bound wrists. One had a dark gray uniform, the other was barefoot. Abandoned weapons mortars were spread over a large area.

Parts of the Marines 1st Division also moved into Iraqi territory overnight, encountering an Iraqi T-55 tank and destroying it with a Javelin, a portable anti-tank missile. Troops from the Army's 3rd Infantry Division destroyed at least three Iraqi armored personnel carriers, front line troops reported by radio.

Elsewhere, U.S. troops met tough resistance. The 7th Marine Infantry's 3rd Batallion apparently had to delay its foray into Iraq after - according to military radios - a large number of previously unknown tanks was sighted on the Iraqi side of the border.

The unit took small arms and artillery fire Thursday night, and at one point a U.S. Cobra helicopter accidentally fired a missile at a U.S. M1 Abrams tank, injuring one soldier and forcing abandonment of the smoldering tank. Friday morning, the unit opened a massive artillery barrage across the border.

There were no other reports of combat casualties. In northern Kuwait, a helicopter crashed Thursday, killing the four American crewmembers and eight British troops on board.

By taking southern Iraq, the allies would command access to the Gulf and set the stage for the first major conquest on the way to Baghdad - Basra, Iraq's second largest city.

The move on the area between Basra and the Persian Gulf suggested that the allied strategy on the ground calls for a two-pronged attack - one to clear Iraqi resistance in the southern oil region while the other charges north toward Baghdad.

Thursday night, the start of the ground advance into Iraq was signalled by a thunderous artillery barrage by allied forces in northern Kuwait across the border. Infantrymen on the move, their weeks of waiting at an end, cheered as shells screamed overhead.

The armored vehicles of the 1st Marine Division rolled across the border at around 9 p.m. local time (1 p.m. EST). As they moved through the desert, burning oil wells were visible, spewing black smoke into skies lit by a nearly full moon.

Earlier Thursday, elite British troops were dropped by Chinook and Sea Stallion helicopters to seize oil facilities in the strategic al-Faw peninsula - Iraq's access point to the Persian Gulf and the site of major oil facilities.

British military officials said they hoped to seize the key port of Umm Qasr, about 20 miles south of Basra.

Through the night and as the sun rose, artillery barrages targeted Iraqi positions in al-Faw, and witnesses in northern Kuwait side said they could hear thunderous explosions from the Umm Qasr area.

Forces continued to mass near the border in northern Kuwait in the morning Friday, preparing to follow into Iraq. The 101st Airborne Division's 3rd Brigade pulled up to a tactical staging area.

"We're poised to do what the 101st does best, air assault," the brigade's commander, Col. Michael Linnington, said.

Conditions were sometimes difficult. The Marines drove through thick, swirling dust storms. Troops detected Iraqi tanks and armored vehicles hidden behind sand berms by the heat they gave off, and U.S. aircraft attacked the positions.

None of the forces apparently encountered chemical or biological weapons. The Marines passed burning oil wells, though it was not known who had set them afire. Flames shot up hundreds of feet, thickening the air with black smoke.

The attack came at the end of a day that began with allied troops at the other end of the gun barrel, as Iraq - responding to the American bombardment of Baghdad and other targets - launched missiles into Kuwait.

The Iraqi military claimed in a statement it had repulsed an "enemy" attack at Al-Anbar province, on Iraq's border with Jordan and Saudi Arabia. It was not clear what force could be attacking from that point, and the statement did not mention attacks in the south.

In the opening barrage Thursday, the 3rd Infantry Division's artillery opened fire on Iraq with Paladin self-propelled howitzers and multiple launch rocket systems. More than 100 artillery shells were fired toward southern Iraq in a five-minute barrage. White light glowed in the sky above the cannons, as explosions were heard from Iraq.

Earlier in the day, the waiting troops had their first brush with action when Iraq fired missiles into Kuwait. There were cries of "gas, gas, gas," and U.S. troops ran for their protective suits and gas masks - but authorities said none of the missiles carried biological or chemical payloads.

Soldiers of A Company, 3rd Battalion, 7th Infantry Regiment were eating lunch when an Iraqi missile hit the desert. They wore the masks for 20 minutes until given the all-clear.

After removing his mask, the company commander, Capt. Chris Carter of Watkinsville, Ga., said: "Saddam is a fool."

"I think it's an obvious attempt by Saddam Hussein to demoralize the army and the American public," Carter said. "An attempt that has been a miserable failure. He's probably got the guys more ready to fight than ever."

Some Marines were simply excited to begin fighting, something they had trained to do for years, and occasional screams of "Let's get it on!" came from some of their weapons holes.

PHOTO CAPTION

Unidentified Iraqi's surrender to British Royal Marines in southern Iraq Friday March 21, 2003 in this television image. U.S. troops advanced through the deserts of southern Iraq in armored convoys Friday after launching the war's ground assault, meeting resistance from Iraqi forces in some areas and soldiers surrendering in others. (AP Photo/POOL)