Fallujah, Iraq ? Striking with overwhelming force on a dusty, moonlit night, U.S. troops Sunday unleashed one of the largest military operations since the fall of Saddam Hussein’s regime, raiding homes and arresting suspected militants in what appears to be the start of a major counterinsurgency campaign in Iraq.

The nationwide sweep, code-named Operation Desert Scorpion, targeted fighters who have been ambushing U.S. soldiers with increasing frequency in recent weeks, especially in the Sunni Muslim center of the country that is viewed as a Saddam stronghold.

More than 1,300 troops from the 2nd Brigade of the 3rd Infantry Division, plus elements of the 101st Airborne Division and various Air Force units, launched a coordinated raid on the notoriously hostile town of Fallujah at 3 a.m. Sunday, breaking down house doors and scaling walls in a surprise assault that left many residents bewildered and embittered.

Similar if much smaller raids took place in the towns of Mosul and Tikrit and in communities west of Baghdad, the military said.

But in a sign that Saddam loyalists remained defiant, unconfirmed news reports indicated guerrillas attacked another U.S. convoy with rocket-propelled grenades Sunday north of Baghdad, setting a truck ablaze. There were reports of several U.S. casualties.

Capt. James Brownlee of the 3rd Infantry Division, assessing the intensive crackdown against armed Iraqi militants, said: “This is the first day of the rest of their lives. We’re here to show them we mean what we say.”

Weapons amnesty

U.S. forces launched the nationwide raids only hours after a weapons amnesty expired at midnight Saturday in Iraq. Few guns had been turned in under the program, which was designed to rid Iraq of armed factions and reduce general lawlessness. Senior U.S. commanders in Iraq had been promising a robust response for days.

In Fallujah, a notorious pro-Saddam enclave 37 miles west of Baghdad, nine men were arrested and hustled away for interrogation, including seven suspected members of the Fedayeen Saddam militia who were sleeping in one building, Brownlee said.

Pipe bombs, blasting caps, communications gear and large quantities of documents also were seized in the raid, he said.

Fallujah has been a hotbed of violent anti-American attacks since U.S. troops killed 14 civilians during a protest march in the town in late April.

Operation Desert Scorpion was launched as a response to those incidents and others north of Baghdad in the so-called “Sunni triangle,” where Saddam, a Sunni, still enjoys considerable support in some communities.

“There have been numerous intelligence reports indicating there would be problems until you achieved stability,” Senate Intelligence Committee Chairman Pat Roberts, R-Kan., said Sunday on CBS’s “Face the Nation.” “I think we will be able to stabilize it over time.”

Roberts and Sen. Carl Levin, D-Mich., who also is on the committee, said that based on the intelligence they had access to there was no evidence Saddam was directing the assaults, or indeed that any one person was responsible.

“It’s mainly Baath Party at this moment,” Levin said. “But there are a lot of other folks involved who are fanatic in their religious views who have also attacked American forces.”

Tanks and teddy bears

Almost 50 U.S. soldiers have died in Iraq since Saddam was toppled by U.S.-led coalition forces two months ago. Pro-Saddam elements and Islamic extremists are blamed for most of the sniping incidents and ambushes, which have been increasingly organized and deadly over the past two weeks.

A major humanitarian campaign designed to win the goodwill of the Iraqi people immediately followed Sunday’s lightning raids.

“We hit them hard and now we’re in the teddy bear phase,” said Sgt. Scott Molina of the 3rd Infantry Division. “We got what we want — the bad guys and intelligence — and now we’re calming people down.”

In Fallujah on Sunday morning, the same heavily armed U.S. troops who had swept through the town’s darkened alleys in Bradley Fighting Vehicles were distributing teddy bears and hundreds of soccer balls to children and free gasoline from 5,000-gallon tankers parked on street corners.

The U.S. Army also was rushing to repaint classrooms and wire the ramshackle town’s long-neglected schools with ceiling fans.

‘Worse than Saddam’

Whether the United States’ new carrot-and-stick approach to pacifying enclaves of violent opposition in central Iraq will work remains to be seen.

Several Fallujah residents expressed deep anger at Sunday’s raid, saying that low-flying helicopters supporting the operation had terrified children. And some claimed that the Americans had been heavy-handed in searching people’s homes, allegedly roughing up suspects and damaging property.

“They acted worse than Saddam’s police,” said Abu Salah Al-Dulaymi, a shopkeeper who said that his neighbor’s home had been raided by mistake. “They treat us like monkeys. Look how they smashed my friend’s door. Who will pay for that?”

Similar complaints from civilians marked an even bigger security sweep last week north of Baghdad dubbed Operation Peninsula Strike.

In that campaign, 4,000 U.S. troops rounded up almost 400 suspected militants from Hussein’s banned Baath Party, including two former generals from the Iraqi army.

But villagers near the town of Balad say five farmers were mistakenly killed by U.S. troops after an ambush Thursday by suspected Fedayeen guerrillas. The U.S. Central Command neither confirmed nor denied the claim.

“We take every precaution to (focus) our forces in these operations,” said the 3rd Infantry Division’s Brownlee.

“We are dealing with small cells, organized cells of anti-coalition elements,” he said. “We will not tolerate them, and this is the first of many operations.”

One of those cells apparently struck back at a U.S. convoy about 40 miles north of Baghdad, the Reuters news agency reported Sunday. Several soldiers were reported injured when a rocket-propelled grenade slammed into a truck.

A spokesman for the U.S. military in Baghdad could not confirm the attack as of late Sunday night.