The latest Pentagon report on the detainee abuse scandal focuses on the role played by military intelligence, which arguably is the branch of the Army most challenged by the insurgency in Iraq.

"MI," as the branch is called inside the Army, generally does not sneak around foreign capitals or conduct other cinematic forms of CIA-style espionage. Its job is the less exotic -- but increasingly difficult -- mission of assessing the capabilities and intentions of the enemy.

In a conventional war, that means counting tanks and divisions, gauging how they are being used tactically, and perhaps guessing at what they might be used to do next.

But in a guerrilla war of the sort the U.S. military is fighting in Iraq, the task is far tougher. The enemy is more elusive. Its numbers matter less than in conventional warfare, although a foe's tactics and weaponry remain an important area of study, especially as insurgents continue probing to find U.S. military vulnerabilities. In Iraq, for instance, the enemy went from direct attacks in the spring of 2003 to lower-profile but deadly approaches such as roadside bombings.

Although the forces supporting rebel Shiite Muslim cleric Moqtada Sadr are fairly visible, said Andrew Bacevich, a retired Army colonel who teaches international relations at Boston University, much less is known about the size, organization or origin of the fighters in the Sunni Muslim part of the country. "We really don't know who the enemy is in the non-Shiite insurgency, or what their aim is, besides forcing the Americans to depart," he said.

Indeed, it was that pressing need to learn more about the insurgency that led Army Lt. Gen. Ricardo S. Sanchez, the U.S. commander on the ground in Iraq then, to push military intelligence officers last summer to make their interrogations more productive. Much of that work went on inside Abu Ghraib prison, where the number of detainees jumped suddenly. Teams of interrogators and translators working under the 205th Military Intelligence Brigade were responsible for extracting information from those prisoners that battlefield commanders could use to thwart attacks and save U.S. troops' lives.

"He was faced with having to develop intelligence so that he could determine why the attacks were occurring, where they were going to occur next and what he could do about it," said Army Gen. Paul J. Kern, who oversaw the report released yesterday. "He put a lot of pressure on his people to get that intelligence."