In the latest sign that troop shortages might be undermining the U.S. occupation of Iraq, the top U.S. commander in the region acknowledged yesterday that too few guards were assigned to Abu Ghraib prison when prisoners were abused there.

Troop shortages "contributed to systemic failures at the prison. I think that's clear," Gen. John P. Abizaid, commander of U.S. force in the Middle East, told the Senate Armed Services Committee.

Abizaid commented in response to a question from Sen. Evan Bayh, an Indiana Democrat, who noted that Abu Ghraib had one-fifth the number of guards called for by Army policy.

Military police officers at the prison have complained that staffing shortages forced them to work extremely long hours with little or no time off. Some have suggested that the resulting stress and exhaustion set the stage for the mistreatment of detainees.

An attorney for Sgt. Javal S. Davis, who is charged with mistreating prisoners and lying to investigators, has said that Davis worked 13 months without a day off. Staff Sgt. Ivan L. "Chip" Frederick II, who is also charged, described in a journal he sent to his family "working a 12 to 14 hour shift ten straight days before getting a day off."

Sen. John McCain, an Arizona Republican, pressed Deputy Defense Secretary Paul Wolfowitz last week on the shortages, saying that "we're paying a very heavy price" for "lack of sufficient troops on the ground."

Yesterday, Abizaid said he thinks there are sufficient combat troops in Iraq but not enough military police to guard prisoners and not enough military intelligence personnel to gather information on the insurgents attacking U.S. forces.

"There are certain types of troops that we don't have enough of, and we still don't have enough of them, and we've got to figure out how to get them," Abizaid said. "And they're MPs, and they're MI guys. ... And they're civil affairs people."

The adequacy of troop strength has been questioned since before the war began last year.

Early warnings

On Feb. 25, 2003, a month before the war began, Gen. Eric K. Shinseki, then the Army chief of staff, told Congress that the complex tasks of safely rebuilding Iraq might require "several hundred thousand" troops.

"Something on the order of several hundred thousand soldiers are probably, you know, a figure that would be required," Shinseki told the same Senate Armed Service Committee. "We're talking about post-hostilities control over a piece of geography that's fairly significant, with the kinds of ethnic tensions that could lead to other problems.

"And so it takes a significant ground-force presence to maintain a safe and secure environment, to ensure that people are fed, that water is distributed, all the normal responsibilities that go along with administering a situation like this."

Two days later, Wolfowitz called Shinseki's estimate "wildly off the mark" and set the tone for far more optimistic projections. In keeping with his thinking, Pentagon planners initially hoped to reduce the number of troops to 30,000 by the end of last summer.

U.S. forces easily toppled the government of Saddam Hussein. But as casualties have grown in the face of a stubborn insurgency, Shinseki has proved prophetic.

First, the Pentagon decided to keep troop strength at 100,000. Last month, commanders decided to keep 135,000 troops in Iraq until the end of next year, and yesterday Abizaid said that might not be enough.

Pressed on the issue yesterday, Abizaid said: "Did I miscalculate the number of troops? Maybe. Maybe I miscalculated, but I think we've adjusted and we'll continue to adjust based on what the enemy does."

Later, Abizaid told the committee that the insurgency can be expected to increase attacks until December and January, when the first Iraqi elections are expected to be held, in an effort to derail the formation of a democratic government for Iraq.

Last month, in a rare public appearance at the University of Georgia, Shinseki, now retired, noted that events have vindicated his predictions.

"My concerns were that this was going to be more difficult than any of us would have liked and was going to take more effort than others might have thought," he said in his address. "The purpose of the military is to create a secure environment for real peace activities. If you do not create this safe environment, there are undesirable others who are only too happy to fill the void."

Lopsided ratios

In a recent interview, a military police officer who worked at the Camp Bucca detention facility in Iraq last year said there were far too few MPs. She said each "compound," with an average of 250 prisoners, was guarded by two MPs from 6 a.m. to 6 p.m. and by two others from 6 p.m. to 6 a.m.

"I think for 250 prisoners we should have had at least four per shift," said the MP, who asked not to be identified. "With two, it was hard to just leave to go to the bathroom. ... The prisoners could have taken over the camp any time they wanted."

The MP said she felt that her superiors tolerated rough treatment of prisoners. On one occasion, when she wrote up a soldier for grabbing a prisoner by the neck and throwing him into a holding cell, she was scolded by her immediate superior and ostracized by other soldiers.

Her supervisor, a police officer in civilian life, told the MPs in his command that he had sometimes broken police department rules and indicated that they might have to do the same in handling Iraqi prisoners.

"He said, "Do what you have to do and I'll back you up," the MP said.