The Army's 3rd Infantry Division and the First Marine Expeditionary Force launched a two-pronged attack toward Baghdad, and both reported breakthroughs as units entered the so-called "red zone" within range of the guns and missiles defending the capital. U.S. officials say Iraqi resistance will be the most tenacious in this zone.
In an attack launched at midnight, 3rd Infantry units surged past the strategic city of Karbala, targeting an estimated 2,000 paramilitary fighters. Karbala, which sits on the main approach to Baghdad from the southwest, was encircled and hit by night-long bombardment from U.S. artillery and warplanes.
Also Wednesday, the 3rd Infantry seized a bridge over the Euphrates River at Mussayib, about 40 miles southeast of Baghdad as it advanced through the Karbala Gap. The bridge, taken with little or no resistance from Iraqi forces, had been rigged with explosives, but engineers defused them.
To the east, thousands of Marines moved against Kut after capturing an important bridge over the Tigris River. Brig. Gen. Vincent Brooks said the Baghdad Division, defending Kut, was destroyed.
For days prior to the offensive, both the Baghdad Division and the Republican Guard's Medina Division defending Karbala had been pounded by airstrikes and artillery barrages. U.S. officials said the bombardment reduced the strength of both divisions by more than 50 percent.
"They're in serious trouble, and they remain in contact now with the most powerful force on Earth," Brooks said of remaining Republican Guard units.
The commander of British forces in Iraq, Air Marshal Brian Burridge, confirmed that the latest assaults by his U.S. allies marked the start of a momentous phase.
"This is certainly a decisive engagement in which we are now just beginning with the Republican Guard," he said.
Still, military officials repeatedly voice worries that Iraq could use chemical or biological weapons against U.S. forces as they close in on the capital.
To reinforce degraded units, Iraqis moved parts of two Republican Guard divisions that normally operate north of Baghdad and near Saddam's hometown of Tikrit to the southern outskirts of the capital.
The Republican Guard forces are the best trained and best equipped in Saddam's military. Still, they've been in decline since losing the 1991 Persian Gulf War and rely on tanks and other heavy weapons that were out of date the first time they faced U.S. forces.
A dozen years of sanctions took their toll, reducing the numbers of Soviet-built tanks the Republican Guards could use and the number of spare parts they could stockpile.
A main question is whether the Republican Guard forces have some of the chemical and biological weapons that U.S. leaders say Saddam is keeping — and whether they could or would use them. Though they have found no chemical weapons, coalition troops searching captured Iraqi areas have found thousands of chemical protective suits and masks as well as nerve agent antidotes and chemical decontamination equipment.
The initial fighting is over terrain where American troops have advantages: Open country and small towns, rather than the urban sprawl of Baghdad. Iraqi officials have said they hope to draw the American forces into urban combat, which is chaotic, difficult and bloody both for military forces and for civilians.
The urban environment shifts some of the advantage to the defender, who can use smaller numbers of fighters sheltered in buildings and underground to pick off invading troops. U.S. military doctrine on urban combat focuses not on the street-by-street fighting Iraq hopes to bring about but on grabbing and holding key areas such as government buildings and military compounds.
In Najaf, about 50 miles south of Karbala, the Central Command said U.S. forces were being fired on from the Ali Mosque, one of the most important Shiite Muslim sites. U.S. commanders say they have been trying to minimize damage to religious sites to avoid angering Muslims in Iraq and abroad.
Iraqi Information Minister Mohammed Saeed al-Sahhaf contended that American warplanes were flying close to some of holiest Muslim sites, causing strong vibrations which could damage the structures.
The coalition has declared the holy sites as "no targets" zones only to be fired upon in self-defense, and troops chose not to return fire Wednesday, Brooks said.
Calling the Iraqi fighters' use of the mosque "a detestable example of putting historical sites in danger," Brooks said coalition troops would try to avoid harming the shrine.
"This regime is firing from within a mosque, something that has no military value, and should be protected by them, but instead it is being protected by us," Brooks said during a briefing at Central Command headquarters.
There have been concerns that Saddam's Sunni Muslim regime would try to provoke U.S.-led forces to attack such holy sites, thereby alienating the country's majority Shiite population, whose support the coalition has been trying to rally. Damage to the shrines could inflame Shiite feelings against the United States worldwide, particularly in Iran.
The International Red Cross, meanwhile, said some its staff members saw the bodies of dozens of people — including women and children — at a town south of Baghdad where Iraqi officials claim U.S. helicopters attacked a residential neighborhood. At least 280 injured people are being treated at a hospital in Hillah, about 60 miles south of Baghdad, the Red Cross said.
Iraqi officials said Tuesday that U.S. Apache helicopters attacked a neighborhood in Hillah, killing 33 people and injuring more than 300. The U.S. Central Command said it was investigating the claim.
Baghdad again came under intense bombardment Wednesday, with telephone exchanges among the targets hit, and again the Iraqi government responded defiantly. Iraqi satellite television broadcast a statement attributed to Saddam declaring that "victory is at hand."
Saddam did not appear in person. U.S. officials say they are not sure whether he is alive and well, wounded from an air strike on one of his bunkers, or dead.