BAGHDAD, Iraq -- The capture of dozens of guerrilla leaders has left the U.S. military with a murky picture of a shadowy resistance here, with American and Iraqi officials divided about whether Iraqis or foreign fighters are responsible for recent attacks.
A spate of arrests -- including the capture of Saddam Hussein -- have broken rebel command networks and forced fighters underground, a top U.S. military official told The Associated Press. Yet attacks persist, crowned by a bold daylight assault this weekend on security compounds in Fallujah that freed 87 prisoners and killed 25 people, mostly police.
U.S. and Iraqi officials have begun focusing on foreign fighters, especially al-Qaida-linked operative Abu Musab al-Zarqawi, a Jordanian blamed for a series of devastating car bombs that U.S. officials say were aimed at fomenting civil war.
"We've really gotten into the guts of the insurgency," said a U.S. military official, who spoke on condition of anonymity. The Dec. 13 capture of Saddam helped the Americans identify and capture a slew of operational-level leaders.
The string of arrests convinced some rebels to give up the fight, while others may have turned to radical politics or religion to undermine the occupation, the official said.
Despite U.S. gains, rebel attacks against U.S. troops in February have increased to between 20 and 24 a day, rising from 18 per day in January.
And guerrilla assaults have grown more spectacular -- and devastating for the Iraqi police, whose death toll appears to have surpassed that of the far more numerous U.S. military forces. At least 538 U.S. troops have died since the U.S. invasion began nearly 11 months ago. But some 600 Iraqi police have been killed since May.
In the Saturday attack in Fallujah, gunmen launched a coordinated, two-pronged assault, pinning down civil defense forces while another group stormed the police station and freed the prisoners. Rebels launched the attack after sealing off the area with checkpoints and warning merchants not to open their shops.
Two days earlier, insurgents showered rocket-propelled grenades and machine gun fire on a convoy carrying two U.S. commanders including John Abizaid, the four-star Army general who runs the war.
That assault came a day after a suicide car bomber killed 47 Iraqis outside an army recruiting center in Baghdad. On Tuesday, a car blast killed 53 outside a police station in the Shiite-majority town of Iskandariyah, south of Baghdad.
The authors of those four attacks remain in dispute.
U.S. officials including Army Brig. Gen. Mark Kimmitt said the "sensational" characteristics of the two suicide bombings pointed to al-Zarqawi, after a letter emerged that intelligence officials say was written by the Jordanian.
In the letter, the author takes credit for 25 suicide operations in Iraq and seeks al-Qaida's help in triggering a civil war by attacking Shiite Muslim leaders and shrines. The United States quickly released a wanted poster of al-Zarqawi with a $10 million bounty.
According to the Brookings Institution's count, Iraq has had 39 suicide bombings since May.
But others say attacks on Iraqi security forces are usually mounted by homegrown insurgents, not foreign terrorists.
In Tuesday's Iskandariyah bombing, Iraqi police Lt. Gen. Ahmed Kadhum Ibrahim said evidence pointed toward an Iraqi's involvement, when investigators traced the engine number of the vehicle used in the blast to one of Saddam's intelligence officers.
A U.S. official in Washington also blamed Saddam loyalists for Wednesday's suicide car blast on a Baghdad recruiting station -- hours after a U.S. Army colonel on the scene said the attack was probably carried out by terrorists intending to show a U.N. mission that Iraq was too unstable for elections.
Saturday's Fallujah attack also inspired contradictory pronouncements.
Administrator L. Paul Bremer told ABC's "This Week" program on Sunday that he believed foreign fighters took part in the attack on the Fallujah police station. Iraqi officials echoed this claim.
However, a senior U.S. military officer discounted the role of foreign fighters saying the "complex, well coordinated attack" appeared to have been the work of former members of Saddam's army or Republican Guard.
"This was something put together by people with knowledge of small-unit tactics," the officer told AP, speaking on condition of anonymity. "This would not be the same tactics that al-Qaida would employ. These are military tactics. It points to former military members."
The competing theories and lack of clear intelligence may stem partially from the U.S. military's success. With their commanders in prison, the loose alliance of guerrilla cells has been disrupted and left leaderless and is fighting "with one arm tied behind their backs," the U.S. military official in Baghdad said.
"Most commanders understood the insurgency would not fade after Saddam was captured, because all knew there were additional elements -- religious extremists, terrorists, criminals, former regimists -- who would continue to fight to gain their own specific form of power within Baghdad," said Brig. Gen. Mark Hertling, a deputy commander of the 1st Armored Division.