NEAR FALLUJAH, Iraq -- Insurgents unleashed attacks yesterday that killed at least 19 Iraqis in Samarra and wounded 20 US troops near Ramadi, in an apparent attempt to spread fighting across the Sunni Muslim heartland ahead of a US assault on their Fallujah stronghold that appeared imminent.
In Fallujah, 11 insurgent groups issued a statement saying they would unite under a single chain of command, called the Islamic Iraqi Armed Forces, to repel the assault, while an influential group that has backed the rebels signaled for the first time a willingness to press its aims through the political process.
The Association of Muslim Clerics, which has repeatedly threatened to boycott national elections scheduled for January, joined other Sunni Muslim and Arab nationalist groups in calling for measures to make the elections fairer for the Sunni minority, said Mohammed al-Qubaisi, a spokesman for the group.
As US forces made final preparations to invade the city, insurgents and their political allies appeared to be making last-ditch efforts to strengthen their negotiating positions or convince US and Iraqi officials that the fight would be bloody and politically costly.
But the assault appeared increasingly likely, as Prime Minister Iyad Allawi scheduled a major address for today and US military commanders reiterated that they would launch the attack at his order. Stepped-up security patrols Friday night and early yesterday brought columns of US M1-A1 tanks, Bradley fighting vehicles, Humvees, and other vehicles within a few hundred yards of houses on the edge of Fallujah, the first close-up glimpse of the city for many of the troops preparing for the assault.
On the dusty US outposts near the city, more than 10,000 troops were readying for the largest battle since the US invasion in March 2003. Soldiers and Marines crowded into extra tents stretching across previously vacant areas; tanks and Humvees were constantly on the move and the skies echoed with mortar and artillery fire and the screech of aircraft.
In the early morning hours yesterday, soldiers of the First Infantry Division looked out over the city from their 69-ton Abrams tanks, their cannons silhouetted against the sky. US commanders believe their troops will have to contend with trenches, concrete barriers, suicide car bombs, and daisy chains of homemade bombs planted in the streets, defenses the insurgents have had six months to plan since taking control in April.
But with nothing moving among the streets of squat rectangular houses, and few lights shining besides the green beacons atop the twin minarets of a mosque, the soldiers wondered among themselves if most of their enemies had fled, as they did ahead of a US assault on Samarra in September.
"Oh, they're there," said Second Lieutenant Andrew Hoeprich, 23, who leads an artillery platoon.
As the soldiers watched, white flashes lit the sky and explosions erupted from the Hay al-Askari neighborhood in the north of the city. An AC-130 Specter gunship slowly circled overhead, and 155mm howitzers fired from a nearby US base.
Red sparks flew into the air as the bombardment triggered secondary explosions, which the soldiers speculated were from arms stockpiles. Phosphorus rounds sent white smoke trails snaking down to the ground and ignited fires. The US military said later that warplanes had dropped five 500-pound bombs on a factory and suspected weapons stores. Fallujah residents reported that the bombing destroyed dozens of houses and a hospital.
The disparate accounts illustrated the challenges the United States and the US-backed government face in making a likely tactical victory into a political win.
US troops are eager to take the city in the hope that it will break the back of the stubborn insurgency that has killed thousands of Iraqis and more than 1,100 Americans, allow reconstruction to start in the city, and make it possible to hold elections there in January.
After learning hard lessons from the repeated failures of Iraqi security forces to hold the city, US commanders have set what they say are realistic goals: US troops will patrol the city to make it safe for a reconstruction effort that will be heavily US-funded but which will be carried out mainly by Iraqi contractors working with Iraqi ministries. US troops will remain until Iraqi forces are ready to take over. They hope the assault will be a showdown that will kill many of the leaders of an insurgency they believe may include 12,000 to 20,000 fighters. Between 1,500 and 5,000 are believed to be in Fallujah.
"The intent is to destroy the organized resistance within the city," said Major John Reynolds, operations officer for a battalion of the First Infantry Divison called in for the fight from its bases east of Fallujah, on the other side of the restive Sunni Triangle. "You exhaust them physically, you exhaust them mentally."
But Reynolds said US troops are fighting an enemy that is extremely sophisticated at using the media and public opinion to gain leverage against a far stronger military force.
He said US military combat cameramen were being sent to the front line "to catch bad guys dropping buildings," in the expectation that insurgents will blow up civilian buildings such as hospitals and schools and blame the devastation on US forces.
"That's his only hope," Reynolds said, adding that insurgents would use images of civilian casualties to press a cease-fire, as they did successfully in April, when US Marines were ordered to attack the city, then ordered to halt when Iraqi politicians and some US allies balked at the reported deaths of hundreds of Fallujans, including many civilians. More than 50 journalists are also embedded with US forces to witness the assault.
For their part, the insurgents' mujahideen shura council yesterday invited media of all nationalities to come to Fallujah "to discover the lives themselves," promising to guarantee their safety. It was not an offer many foreign journalists were likely to accept after a string of kidnappings of reporters and other civilians, some of whom have been beheaded by Fallujah-based groups.
On Friday, the holiest day of the week for Muslims, the imam at Fallujah's main Al Khadra al-Mohammadiya mosque taunted the Americans with a reference to Saddam Hussein's suspected chemical and biological weapons, which were the stated reason for the US invasion but have not been found. He said that Abu Musab al-Zarqawi, the Jordanian who has claimed responsibility for many of Iraq's worst suicide bombings, and who US officials say is based in Fallujah, could prove just as elusive.
"What will become of their credibility before the Iraqi and the American people if they go into Fallujah and do not find or kill Zarqawi?" the preacher said. "Will it be just like the weapons of mass destruction?"
But the mosque, which normally holds several thousand people, had only 200 worshipers, half affiliated with the insurgency, according to an Iraqi journalist who attended. Most of Fallujah's 250,000 to 300,000 people have fled; police have told the rest to stay inside with their lights out.
At the main base near Fallujah, US troops bent over maps and plans carried out last-minute maintenance and talked about the challenges ahead.
Most believed the fight would be far tougher than in Samarra, where most insurgents fled, or in Najaf, where residents largely supported the effort to drive out the rebel cleric Moqtada al-Sadr, whose fighters were better organized than expected but less armed than the Fallujah rebels.
"They've owned the ground since April," said Major General Richard Natonski, who will direct the operation as commander of the First Marine Expeditionary Force's First Regimental Combat Team.
"It's going to be hot," said Sergeant First Class James Woody, who commands an M1-A1 tank with "Anger Management" stenciled on the barrel of the main gun.
Tank commanders say it will be a challenge to maneuver their heavy armor in Fallujah's narrow streets -- a kind of fight the US military has not engaged in since World War II. Heavy urban fighting was expected in Baghdad during the invasion, but did not materialize when Hussein's forces quickly folded.
Commanders warned their men to be particularly vigilant when firing heavy weapons in the city, since they will be working in close quarters and there is a high risk of friendly fire.
Another challenge will be working with Iraqi security forces, whose participation is essential to make the battle politically palatable.
But Iraqi forces are widely mistrusted by front-line commanders at the battalion and company level, who have frequently found them unreliable.
The Iraqi forces being brought into Fallujah belong to new elite units of Iraq's national army; there will be less reliance on the Iraqi National Guard, whose performance has been spotty.
Another problem is that some insurgents will probably wear the same uniforms as Iraqi government forces, a legacy of the Fallujah Brigades, the force that Marines hired, equipped, clothed, and trained in April but which turned out to be dominated by insurgents.
If there is limited fighting, that could also be a problem, if it means insurgents have chosen to pull back rather than be wiped out, as they did in Samarra, 60 miles northeast of Fallujah.
Violence flared again in Samarra yesterday, a month after US forces declared it back under Iraqi government control. Militants stormed a police station, killing 12 policemen and injuring one.
Two other suicide bombs went off, one near the mayor's office, and a mortar shell fell on a crowded market. At least 21 people were killed and 22 wounded, the Associated Press reported.
In Ramadi, Fallujah's sister city to the west, police told Reuters a suicide car bomber drove into a convoy of US troops. The US military said 20 were wounded in an attack there.
Globe correspondent Sa'ad al-Izzi contributed to this story from Baghdad. Barnard and an Iraqi Globe correspondent contributed from Fallujah.