Some former task force members said the Nama in the camp's name stood for a coarse phrase that soldiers used to describe the compound. One Defense Department specialist recalled seeing pink blotches on detainees' clothing as well as red welts on their bodies, marks he learned later were inflicted by soldiers who used detainees as targets and called themselves the High Five Paintball Club.

Mr. McGraw, the military spokesman, said he had not heard of the Black Room or the paintball club and had not seen any mention of them in the documents he had reviewed.

In a nearby operations center, task force analysts pored over intelligence collected from spies, detainees and remotely piloted Predator surveillance aircraft, to piece together clues to aid soldiers on their raids. Twice daily at noon and midnight military interrogators and their supervisors met with officials from the C.I.A., F.B.I. and allied military units to review operations and new intelligence.

Task Force 6-26 was a creation of the Pentagon's post-Sept. 11 campaign against terrorism, and it quickly became the model for how the military would gain intelligence and battle insurgents in the future. Originally known as Task Force 121, it was formed in the summer of 2003, when the military merged two existing Special Operations units, one hunting Osama bin Laden in and around Afghanistan, and the other tracking Mr. Hussein in Iraq. (Its current name is Task Force 145.)

The task force was a melting pot of military and civilian units. It drew on elite troops from the Joint Special Operations Command, whose elements include the Army unit Delta Force, Navy's Seal Team 6 and the 75th Ranger Regiment. Military reservists and Defense Intelligence Agency personnel with special skills, like interrogators, were temporarily assigned to the unit. C.I.A. officers, F.B.I. agents and special operations forces from other countries also worked closely with the task force.

Many of the American Special Operations soldiers wore civilian clothes and were allowed to grow beards and long hair, setting them apart from their uniformed colleagues. Unlike conventional soldiers and marines whose Iraq tours lasted 7 to 12 months, unit members and their commanders typically rotated every 90 days.

Task Force 6-26 had a singular focus: capture or kill Mr. Zarqawi, the Jordanian militant operating in Iraq. "Anytime there was even the smell of Zarqawi nearby, they would go out and use any means possible to get information from a detainee," one official said.

Defense Department personnel briefed on the unit's operations said the harsh treatment extended beyond Camp Nama to small field outposts in Baghdad, Falluja, Balad, Ramadi and Kirkuk. These stations were often nestled within the alleys of a city in nondescript buildings with suburban-size yards where helicopters could land to drop off or pick up detainees.

At the outposts, some detainees were stripped naked and had cold water thrown on them to cause the sensation of drowning, said Defense Department personnel who served with the unit.

In January 2004, the task force captured the son of one of Mr. Hussein's bodyguards in Tikrit. The man told Army investigators that he was forced to strip and that he was punched in the spine until he fainted, put in front of an air-conditioner while cold water was poured on him and kicked in the stomach until he vomited. Army investigators were forced to close their inquiry in June 2005 after they said task force members used battlefield pseudonyms that made it impossible to identify and locate the soldiers involved. The unit also asserted that 70 percent of its computer files had been lost.

Despite the task force's access to a wide range of intelligence, its raids were often dry holes, yielding little if any intelligence and alienating ordinary Iraqis, Defense Department personnel said. Prisoners deemed no threat to American troops were often driven deep into the Iraqi desert at night and released, sometimes given $100 or more in American money for their trouble.

Accusations of abuse by Task Force 6-26 came as no surprise to many other officials in Iraq. By early 2004, both the C.I.A. and the F.B.I. had expressed alarm about the military's harsh interrogation techniques.

The C.I.A.'s Baghdad station sent a cable to headquarters on Aug. 3, 2003, raising concern that Special Operations troops who served with agency officers had used techniques that had become too aggressive. Five days later, the C.I.A. issued a classified directive that prohibited its officers from participating in harsh interrogations. Separately, the C.I.A. barred its officers from working at Camp Nama but allowed them to keep providing target information and other intelligence to the task force.

The warnings still echoed nearly a year later. On June 25, 2004, nearly two months after the disclosure of the abuses at Abu Ghraib, an F.B.I. agent in Iraq sent an e-mail message to his superiors in Washington, warning that a detainee captured by Task Force 6-26 had suspicious burn marks on his body. The detainee said he had been tortured. A month earlier, another F.B.I. agent asked top bureau officials for guidance on how to deal with military interrogators across Iraq who used techniques like loud music and yelling that exceeded "the bounds of standard F.B.I. practice."

American generals were also alerted to the problem. In December 2003, Col. Stuart A. Herrington, a retired Army intelligence officer, warned in a confidential memo that medical personnel reported that prisoners seized by the unit, then known as Task Force 121, had injuries consistent with beatings. "It seems clear that TF 121 needs to be reined in with respect to its treatment of detainees," Colonel Herrington concluded.

By May 2004, just as the scandal at Abu Ghraib was breaking, tensions increased at Camp Nama between the Special Operations troops and civilian interrogators and case officers from the D.I.A.'s Defense Human Intelligence Service, who were there to support the unit in its fight against the Zarqawi network. The discord, according to documents, centered on the harsh treatment of detainees as well as restrictions the Special Operations troops placed on their civilian colleagues, like monitoring their e-mail messages and phone calls.

Maj. Gen. George E. Ennis, who until recently commanded the D.I.A.'s human intelligence division, declined to be interviewed for this article. But in written responses to questions, General Ennis said he never heard about the numerous complaints made by D.I.A. personnel until he and his boss, Vice Adm. Lowell E. Jacoby, then the agency's director, were briefed on June 24, 2004.

The next day, Admiral Jacoby wrote a two-page memo to Mr. Cambone, under secretary of defense for intelligence. In it, he described a series of complaints, including a May 2004 incident in which a D.I.A. interrogator said he witnessed task force soldiers punch a detainee hard enough to require medical help. The D.I.A. officer took photos of the injuries, but a supervisor confiscated them, the memo said.

The tensions laid bare a clash of military cultures. Combat-hardened commandos seeking a steady flow of intelligence to pinpoint insurgents grew exasperated with civilian interrogators sent from Washington, many of whom were novices at interrogating hostile prisoners fresh off the battlefield.

"These guys wanted results, and our debriefers were used to a civil environment," said one Defense Department official who was briefed on the task force operations.

Within days after Admiral Jacoby sent his memo, the D.I.A. took the extraordinary step of temporarily withdrawing its personnel from Camp Nama.

Admiral Jacoby's memo also provoked an angry reaction from Mr. Cambone. "Get to the bottom of this immediately. This is not acceptable," Mr. Cambone said in a handwritten note on June 26, 2004, to his top deputy, Lt. Gen. William G. Boykin. "In particular, I want to know if this is part of a pattern of behavior by TF 6-26."

Military and legal experts say the full breadth of abuses committed by Task Force 6-26 may never be known because of the secrecy surrounding the unit, and the likelihood that some allegations went unreported.

In the summer of 2004, Camp Nama closed and the unit moved to a new headquarters in Balad, 45 miles north of Baghdad. The unit's operations are now shrouded in even tighter secrecy.

Soon after their rank-and-file clashed in 2004, D.I.A. officials in Washington and military commanders at Fort Bragg agreed to improve how the task force integrated specialists into its ranks. The D.I.A. is now sending small teams of interrogators, debriefers and case officers, called "deployable Humint teams," to work with Special Operations forces in Iraq and Afghanistan.

Senior military commanders insist that the elite warriors, who will be relied on more than ever in the campaign against terrorism, are now treating detainees more humanely and can police themselves. The C.I.A. has resumed conducting debriefings with the task force, but does not permit harsh questioning, said a C.I.A. official.

General McChrystal, the leader of the Joint Special Operations Command, received his third star in a promotion ceremony at Fort Bragg on March 13.

On Dec. 8, 2004, the Pentagon's spokesman, Lawrence Di Rita, said that four Special Operations soldiers from the task force were punished for "excessive use of force" and administering electric shocks to detainees with stun guns. Two of the soldiers were removed from the unit. To that point, Mr. Di Rita said, 10 task force members had been disciplined. Since then, according to the new figures provided to The Times, the number of those disciplined for detainee abuse has more than tripled. Nine of the 34 troops disciplined received written or oral counseling. Others were reprimanded for slapping detainees and other offenses.

The five Army Rangers who were court-martialed in December received punishments including jail time of 30 days to six months and reduction in rank. Two of them will receive bad-conduct discharges upon completion of their sentences.

Human rights advocates and leading members of Congress say the Pentagon must still do more to hold senior-level commanders and civilian officials accountable for the misconduct.

The Justice Department inspector general is investigating complaints of detainee abuse by Task Force 6-26, a senior law enforcement official said. The only wide-ranging military inquiry into prisoner abuse by Special Operations forces was completed nearly a year ago by Brig. Gen. Richard P. Formica, and was sent to Congress.

But the United States Central Command has refused repeated requests from The Times over the past several months to provide an unclassified copy of General Formica's findings despite Mr. Rumsfeld's instructions that such a version of all 12 major reports into detainee abuse be made public.

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