U.S. and British forces streamed in a long line of tanks and armored vehicles toward Basra, Iraq's second largest city, on Saturday, a day after they collected underfed and overwhelmed Iraqi soldiers who surrendered in droves.

An entire Iraqi division, the 51st Infantry, gave up to U.S. troops Friday, military officials said. A key unit for Basra's defense with 8,000 men and up to 200 tanks, it was the largest defection in a day when Saddam Hussein's forces showed signs of crumbling.

Saturday morning, American Marines and British troops rumbled along the main road from the Kuwaiti border to Basra, Highway 80 -- nicknamed the "Highway of Death" during the 1991 Gulf War when U.S. airstrikes wiped out an Iraqi military convoy along it.

At the Kuwait border, hundreds of tanks, armored personnel carriers, Humvees and trucks were lined up Saturday in a desert muddied by overnight rain, waiting in columns to pass into Iraq. It resembled a great train yard in the desert -- some lines 70 vehicles long, others 50 long.

In the wake of the allied force, Iraqi captives were left packed into improvised pens of concertina wire, watched over by Marines. Partly disassembled rifles taken from the surrendering soldiers were piled beside the road.

The surrendering soldiers were not the fabled and well-fed Republican Guardsmen who anchor Saddam's defense. For the most part, these were a rag-tag army, many of them draftees, often in T-shirts. Their small arms could accomplish little against opposing forces wielding 21st century weaponry.

"A lot of them looked hungry. They haven't been fed in a while," said one U.S. military official, speaking on condition of anonymity.

Basra appeared to be the next main objective after U.S. Marines and their allies seized the strategic port city of Umm Qasr and with it, Iraq's access to the Persian Gulf, as well as the key oil facilities on the al-Faw peninsula and many of southern Iraq's oil fields.

At the same time, the Army's 3rd Infantry Division surged 100 miles into Iraq, moving in the desert parallel to the Euphrates River. It avoided the populated river valley and flanked Iraqi units, going straight for the Republican Guard around Baghdad.

The Army's 101st Airborne Division also joined the fight, and much more was to come -- an extraordinary land-based armada of allied weaponry and troops was caught in an enormous traffic jam in Kuwait, ready to strike when it could cross the border.

There were pockets of resistance, some of it stiff, with Iraqis fighting with small arms, pistols, machine guns and rocket-propelled grenades. A second combat death was reported Friday, a member of the 1st Marine Expeditionary Force who was wounded while battling a platoon of Iraqi infantry.

Australian commandos, who have been operating deep in Iraq, destroyed a command and control post and killed a number of soldiers, according to the country's defense chief, Gen. Peter Cosgrove.

But often, the opponent advanced with a white flag in hand, instead of a rifle.

Within a few hours of crossing into southern Iraq, the 15th Marine Expeditionary Unit encountered 200 or more Iraqi troops seeking to surrender. One group of 40 Iraqis marched down a two-lane road toward the Americans and gave up.

Another group of Iraq soldiers alongside a road waved a white flag and their raised hands, trying to flag down a group of journalists so they could surrender.

Forty to 50 Iraqi soldiers surrendered to a Marine traffic control unit. They came down the road in the open back of a troop vehicle, their hands in the air for about a mile before they reached the Marines.

Their decision to give up was not unexpected, or unprompted; for months, Iraq has been bombarded with messages from the Americans, urging its soldiers to refuse to fight.

At a Pentagon news conference, Defense Secretary Donald H. Rumsfeld called on Iraq's military to "do the honorable thing, stop fighting that you may live to enjoy a free Iraq, where you and your children can grow and prosper."

Rumsfeld said the allied forces were advancing, and now controlled "a growing portion of the country of Iraq." The captured territory included two airfields in western Iraq.

Lt. Cmdr. Mark Johnson, a pilot returning to the USS Kitty Hawk from a mission over southern Iraq, said it appeared that Iraqi forces were withdrawing in front of advancing U.S. forces. He could see columns of Marines moving but "there was nobody coming south to meet them."

Time and again, he said, he was told to ignore targets like missile launch sites because U.S. troops had passed without any opposition.

"As it turned out, there was nobody to drop bombs on tonight," Johnson said. "It was simply because we had already taken that land," he said. "There was no need to bomb any more."

The ground campaign appeared to be moving faster than planned. Units reached locations in Iraq 24 hours ahead of their expected arrival time, according to several reporters attached to those units.

The bulk of the allied force hadn't even entered Iraq yet.

There was a huge traffic jam at the border -- thousands of vehicles parked in parallel rows, nothing but columns of trucks, Humvees, oil tankers, flatbed tucks, armored vehicles and vehicles of every stripe, from horizon to horizon. The traffic was so bad that it took 6 hours for one unit to go 51 miles, in swirling dust.

Crossing the border Friday morning, the 3rd Battalion of the 7th Marine Infantry faced little resistance. Tanks attached to the battalion attacked five Iraqi tanks just north of the border, destroying them easily.

The battalion passed the brown, stone rubble of several buildings it had shelled just minutes before -- the air still held the acrid smell of explosives -- and at least five enormous pictures of a smiling Saddam Hussein, some with him wearing a robe, others with him in a headscarf, that stood intact at the border post.

They reached the town of Safwan, where speakers warned Iraqis to stay out of the Marines' way. A few ventured outside: A man on the side of the road bearing a white flag. Another in a long, gray robe, prostrate on the ground, apparently in prayer.

"I never thought I'd see this place," said Cpl. Matt Nale, 31, of Seattle.

The Marines later took control of positions mostly abandoned by Iraq's 32nd Mechanized Infantry Brigade, blowing up a few abandoned tanks and armored personnel carriers and engaging in short firefights with a few Iraqi soldiers who had stayed back to defend their headquarters and barracks or were unable to flee in time.