U.S. PUMMELS BAGHDAD AS TROOPS PUSH TOWARD CITY

The United States launched an intense and long-threatened aerial assault against Iraq on Friday, raining hundreds of bombs and cruise missiles on the capital and other places deemed crucial to President Saddam Hussein’s regime.

The airstrikes, which the military had dubbed a campaign of “shock and awe,” were launched as tens of thousands of heavily armed U.S. and British ground troops raced across the Iraqi desert in a linear dust cloud pointed at Baghdad.

Although resistance was only sporadic, the United States suffered its first combat casualties of the war when two Marines were killed in separate firefights in southern Iraq, not far from the Kuwaiti border.

Early today, two British Sea King helicopters collided over the Persian Gulf, killing all seven crew members, including an American naval officer, British military sources said in Doha, Qatar.

In Baghdad, explosions shook the capital continuously for more than two hours, beginning just after nightfall and lighting the sky with billowing plumes of fire, smoke and debris.

Among the sites hit were Hussein’s presidential palace compound, the headquarters of the Special Security Organization and barracks of the Republican Guard. The number of casualties was not immediately known.

Senior U.S. officials said an even heavier bombardment was planned for today. At dawn, three big explosions shook Baghdad.

There was no immediate indication that Friday’s attack had dislodged the Iraqi leadership, but there were hints of cracks.

In the south, the Iraqi army’s entire 51st Mechanized Division, consisting of 8,000 troops, surrendered to U.S. Marines, defense officials said, and hundreds of other soldiers have given themselves up elsewhere.

Some Iraqi commanders reportedly have abandoned their troops.

“With leadership like that, it’s no surprise they don’t want to fight,” said Capt. Joe Plenzler, with the 1st Marine Division.

In the village of Safwan, on the Iraqi side of the Kuwaiti border, civilians greeted U.S. Marines with cheers and joined them in gleefully tearing down posters of Hussein.

Perhaps more significant, an official at the U.S. Central Command in Doha said an estimated 20% of the Republican Guard -- the troops considered most loyal to Hussein -- either had defected or planned to defect in the coming days.

The official, speaking on condition of anonymity, said the estimate was based on conversations U.S. and British forces have had with selected Republican Guard commanders, some of whom are being offered a role in rebuilding the country.

Another senior U.S. military official, who also insisted that he not be named, said the aerial bombardment over the next 24 hours would focus on obliterating the top-tier forces, as well as disabling the Iraqi leadership’s ability to communicate with its military and the nation at large.

U.S. intelligence officials said they still do not know whether Hussein or his sons were injured or killed in the predawn strike outside Baghdad on Thursday that was the opening salvo of the war.

“We continue to believe they were in the compound,” one U.S. official said.

“There’s conflicting reports about whether they were killed or injured.”

The official said other countries claim to have fielded reports that Hussein was killed. He declined to name the countries. But he said the United States had been unable to corroborate the information.

Iraqi TV continued to broadcast Friday, and telephones in Baghdad were working.

But Defense Secretary Donald H. Rumsfeld suggested that Iraqi military communications might already be disintegrating.

“The regime is starting to lose control of their country,” he said. “Their ability to see what is happening on the battlefield, to communicate with their forces and to control their country is slipping away.”

Rumsfeld insisted that the United States was taking unprecedented measures to minimize civilian deaths by pinpointing government targets.

“Every single target has been analyzed, and the weapon has been carefully selected, and the direction in which the weapon is delivered has been carefully examined, and the time of day when there is the greatest prospect of minimizing any innocent lives,” Rumsfeld said.

Publicly, at least, Iraqi officials were insistent that they were in control and would prevail.

“You will see in the next few days that our victory is certain, certain, certain,” said Interior Minister Mahmud Dhiyab Ahmad. Iraqi officials said that during the first day of bombing, one woman was killed and 14 civilians injured. They listed military casualties as four killed and six wounded and said 72 bombs and missiles had landed.

The United States said American and British aircraft had flown more than 1,000 bombing sorties and launched 1,000 cruise missiles Friday alone.

“We’re into this now,” Rear Adm. John M. Kelly, battle group commander, told reporters aboard the aircraft carrier Abraham Lincoln, his flagship in the Persian Gulf. “We’re gonna win it and win it fast.”

Though there were setbacks, Pentagon officials said the ground campaign was advancing ahead of schedule. They said the Army’s 3rd Infantry Division, with its fast-moving Abrams battle tanks and Bradley fighting vehicles, could reach Baghdad as soon as Monday.

As the Army moved north of the Saudi border toward Baghdad, U.S. and British marines drove through the Euphrates Valley after capturing the Iraqi port of Umm al Qasr and the Al Faw peninsula. Their objective was to speed toward the capital, and they sought to avoid encumbering themselves with battles en route where there was little resistance.

Follow-up forces, possibly including military police, were expected to maintain a presence to prevent Iraqis from threatening coalition troops and to distribute food, medicine and other humanitarian supplies. As the Marines move northward, units behind them are expected to take the waterways, clear mines and ship military and humanitarian supplies north.

With Republican Guard troops concentrated around Baghdad and farther north in Hussein’s hometown of Tikrit, U.S. Marine and Army mechanized units engaged in scattered firefights but faced little resistance, defense officials said. There is little sense in striking peripheral targets, a senior military official said.

“The Iraq center of gravity is Baghdad,” he said.

By Friday night, U.S. forces had advanced about 100 miles into Iraq from Kuwait, according to Air Force Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff. American troops, he said, had seized territory in southern, western and northern Iraq. The U.S. troop presence in the north remained small and was limited to Special Forces, he said.

U.S. troops seized two airfield complexes in far western Iraq without much resistance, military officials said. The airfields are important in part because they are believed to be repositories for Iraqi missiles. However, U.S. officials said they had only “tentative” control of the installations.

Myers said the troops also had secured the main oil facilities along the Al Faw waterway, Iraq’s lifeline to the Persian Gulf. Marine units seized numerous oil fields in southern Iraq to prevent Iraqi forces from setting them afire, officials said. Iraqi soldiers are believed to have set several wells on fire Thursday.

One senior Pentagon official said civilians who specialize in fighting oil fires are moving in behind U.S. forces to begin extinguishing the blazes.

In London, Adm. Sir Michael Boyce, chief of the British defense staff, said two British battle groups had flanked U.S. troops and reached the outskirts of Basra, Iraq’s second-largest city. As the center of Iraq’s Shiite Muslim majority, Basra is expected to welcome the overthrow of Hussein’s Sunni-dominated government.

The air campaign Friday was the most intense and sophisticated in U.S. military history, one American defense official said.

More than 2,000 sorties were flown by warplanes, including F-117s, B-2, B-52 and B-1 bombers, A-10s and Navy strike aircraft, the official said. Bombs were dropped by about half the planes, with the remainder carrying out intelligence, surveillance, interdiction, refueling and special operations.

The bombs hit more than 1,500 targets, the official said, in some cases hitting a single building with as many as 10 bombs.

The strikes were against Iraqi air defense systems, command and control centers, security operations, leadership compounds and sites where Iraq was believed to be developing proscribed weapons, the official said.

Rumsfeld said earlier in the day that military planners have been working for months to assign the appropriate precision-guided munition for each target.

A military official said U.S. planes were not challenged by any Iraqi aircraft but did encounter “heavy defenses” from Iraqi surface-to-air missiles and antiaircraft artillery fire. No planes were lost.

U.S. aircraft flew from 30 air bases in a dozen countries, plus five aircraft carriers. Planes took off from as far away as Whiteman Air Force Base in Missouri, a 34-hour round trip.

President Bush expressed pleasure at the course of events Friday.

“We’re making progress,” he said as he met with congressional leaders in the Oval Office. “We will stay on task until we’ve achieved our objective, which is to rid Iraq of weapons of mass destruction and free the Iraqi people so they can live in a society that is hopeful and democratic and at peace in its neighborhood.”

The president offered his condolences to the families of the troops killed in battle and his gratitude to those doing the fighting.

“All of us involved here in Washington are extremely proud of the skill and bravery of our young Americans, who are willing to sacrifice for something greater than themselves,” Bush said.

The president watched televised images of some of the bombardment of Baghdad from the Oval Office, aides said. He later left the White House to spend the weekend at Camp David, the presidential retreat in Maryland.

Protests against the U.S.-led invasion spread through several Arab capitals, with as many as 40,000 demonstrators marching in Cairo. French and Russian officials also spoke out against the war. “I personally view the military operation as illegal,” Russian Foreign Minister Igor S. Ivanov told the State Duma, the lower house of parliament.

Besides Baghdad, targets of the aerial campaign included sites in the north of Iraq: the oil city of Kirkuk, and territory held by Ansar al-Islam, a militant Muslim group.

Kirkuk, which produces a third of Iraq’s oil supply, is crucial to stability in the region, and U.S. ground forces, despite the lack of a northern front, were expected to move quickly to secure the city’s 300 wells.

The strikes on Ansar, which the Bush administration labeled a terrorist organization last month, was a sign that Washington is intent on preventing the spread of Islamic radicalism.

One potential roadblock in the U.S. campaign against Iraq fell late Friday when, after a day of tense bargaining, Turkey agreed to open two air corridors for allied aircraft, enabling U.S. and British bombers to begin striking Iraq from the north.

But a potential conflict emerged when Turkey sent at least 1,000 soldiers over the border into Kurdish-held territory in northern Iraq.

Turkish television reports said the air clearance was effective immediately, with one route following the Black Sea coast and the other along Turkey’s southern border.

Turkey’s parliament had authorized the overflights Thursday, but the government held up final approval as it tried to get the Bush administration to stop objecting to the planned Turkish army intervention in northern Iraq’s Kurdish-run enclave. Secretary of State Colin L. Powell rejected that condition, insisting that the two issues be resolved separately.

The United States and its Kurdish allies in northern Iraq have warned Turkey that any intervention by its army could result in clashes with their forces.

“You can be certain that we have advised the Turkish government and the Turkish armed forces that it would be notably unhelpful if they went into the north in large numbers,” Rumsfeld said Friday.

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Daniszewski reported from Baghdad and Schrader from Washington. Contributing to this report were Times staff writers Richard Boudreaux in Ankara, Turkey; Robin Wright, Maura Reynolds, Greg Miller and John Hendren in Washington; Tony Perry in southern Iraq; Jeffrey Fleishman in northern Iraq; Carol J. Williams aboard the carrier Abraham Lincoln; Tracy Wilkinson and Tyler Marshall in Doha, Qatar; and special correspondent William Wallace in London.