ASIRIYA, Iraq, March 23 ? What looked to be an easy ride into this city turned into a messy firefight today when Iraqi tanks, regular soldiers and guerrillas darted through the streets and turned their mortars, artillery cannons, rockets and rifles on advancing United States marines.
 
The battle began shortly after dawn. The infantry unit, code-named Timber Wolf, approached the southern edge of Nasiriya, which straddles the Euphrates River in the south. The city's bridges, which were eventually captured, are essential to the allied troops behind Marine Task Force Tarawa, who are looking to head north, toward Baghdad.  
 
The marines were trying to secure the bridges and retrieve four wounded Army soliders. The soldiers were among those left stranded after about a dozen members of their unit were killed or captured after making a wrong turn while trying to skirt the city before dawn.
 
Still, there was little clue what was in store for the marines ? the deadliest battle of the war so far.  
 
Minutes before 7 a.m., Col. Glenn Starnes, commanding officer of the artillery battalion, listening on a radio several miles south, shouted, "Timber Wolf is taking fire!"
 
Tanks, part of a light armor reconnaissance unit, crept forward 100 yards at a time against pockets of Iraqi infantry and bands of Iraqi guerrillas known as Martyrs of Saddam.  
 
The battle continued throughout the afternoon, with as many as 10 marines killed and dozens wounded. The Marine artillery unit, trying to provide cover fire for the tanks, spent frustrating hours unable to shoot into the city for fear of hitting fellow marines. Iraqi mortar fire sounded in the distance, and Colonel Starnes winced and cursed as American cannon batteries, caught off guard, scrambled to get into position. Twenty-three minutes later, the first battery reported itself "fully in the fight," or ready to fire.
 
Radar detected the location of the Iraqi mortars, and the Marine cannons returned fire, but it was impossible to tell what was hit. Mortars are easy to move and hide, especially in a city, where the shooter can drag the weapon around a corner or into a home and shut the door in seconds.  
 
"You've got to remember," Maj. Phillip Boggs said, "you can hide a mortar in nothing."
 
The American command center was code-named Nightmare. On its maps, it appeared that besides mortar, up to four Iraqi tanks were shooting from behind a building.
 
"Waste it," an officer said under his breath, wanting to demolish the site. But firing would have been too dangerous with so little information about the target.
 
With every "denied" spoken over the artillery radios, curses followed and the unit was forced to hold its fire.  
 
"Let's not get gun-happy here," Major Boggs cautioned the officers under the tarp that was the command center, quickly heating under the midmorning sun.  
 
"We are running amok," he said. "We're suppressing him, probably, but we're not killing him."
 
Reports came in of a platoon-sized group of 30 or 40 Iraqis, and smaller squads of soldiers apparently from Iraq's 11th Mechanized Infantry Division. The leadership of the division reportedly surrendered to Army units the day before. But marines approaching the city found machine gun nests in outlying dwellings, Colonel Starnes said.
 
They also found four Army soldiers, injured in a ditch, and called in an evacuation team. The soldiers were part of a group of about 20 that made a wrong turn in the dark, intending to skirt the city, only to be ambushed, Colonel Starnes said.  
 
There was a puzzle. The Iraqi mortar and artillery fire missed by such large distances that the marines wondered about another motivation behind the rounds.
 
"I'm afraid he's trying to unmask me," Colonel Starnes said. "I'm afraid he's trying to find out where we're at." Returning fire, he feared, could give away his position.  
 
A leutenant, Michael Slawsky, said, "It would be really nice to have some forward observer out there to tell us `left' or `right' or whatever, and what we hit."
 
After being pinned down most of the morning, the infantry unit and the forward observer for the artillery advanced shortly before noon, meeting machine-gun fire.
 
The fight did not let up. Cobra helicopters flew low, barely above the oversized balloons regularly launched by an artillery unit to test the wind. More than a dozen marines shouted orders and scribbled down coordinates, hunched over lunchbox-sized portable telephones, often struggling to be heard above the din.  
 
The phone boxes frequently went silent for no apparent reason. Officers wiggled the cables or clicked the button on the handset, or picked up the box and slammed it down on the table until it worked again.
 
With the heat came the flies. The voices on the other end of the radio sounded frantic, shouting above machine-gun fire in the background. Tensions rose quickly in Nightmare. The men under the tarp snapped and swore at one another.
 
One marine berated a communications officer, asking him how he would feel if he were being shot at in the streets and could not reach the artillery batteries.
 
The afternoon brought news that was both good and terrible. Timber Wolf, the infantry unit, had captured the bridges and advanced north of the city. The artillery batteries, finally granted permission to fire, lobbed rounds of powerful explosives at the black circles that had been on their laminated maps for hours.
 
Later, the artillery battalion received notice that it would accept the wounded and perhaps dead marines from the Nasiriya fight. Medical trucks and doctors hurried to the square of desert, past the ring of perimeter guards.
 
"The bridge is considered secured," Major Boggs said when the second of the two was captured.
 
"It is," Colonel Starnes replied, "but I wouldn't want to drive on it."