The Marine Corps relieved one of its top commanders in Iraq yesterday, an extremely unusual action, especially for a unit engaged in combat.

Col. Joe W. Dowdy has been the officer in charge of the 1st Marine Regiment, one of the three major Marine Corps ground units fighting toward Baghdad. His regiment is reported to have been used to pin down Republican Guard units in the city of Kut while the other two major units, the 5th and 7th Marines, crossed the Tigris River on Thursday and raced toward Baghdad. Those units encountered heavy ground fighting yesterday on the outskirts of the capital and had at least three M1 tanks disabled by Iraqi fire.

The U.S. military was unusually guarded about discussing the reason for the battlefield removal. The Central Command, the U.S. military headquarters for the war, announced the action but offered no explanation for it. Pentagon spokesmen referred questions to the Marine Corps, which had no comment.

"We can confirm that he has been relieved," said Marine Maj. Brad Bartelt, a Central Command spokesman. "I have no other information at this time."

At Kut, 100 miles southeast of Baghdad, the 1st Marine Regiment's mission included feinting a move toward Iraqi positions in such a way as to draw artillery fire, according to a Marine officer. That maneuver was intended to expose the locations of the Iraqi gun batteries, which could then be hit by airstrikes. The Iraqi units didn't take the bait and never opened fire, the officer said.

Dowdy's immediate superior, Maj. Gen. James N. Mattis, the commander of the 1st Marine Division, has the reputation of being an extremely aggressive commander, which is regarded as a plus in the Corps.

Allan Millett, a military historian at Ohio State University and a retired colonel in the Marine Corps Reserve, said that "relieving a regimental commander for cause is unusual, in combat or not." The move is especially significant because the three Marine regiments in Iraq have been operating in a decentralized manner -- that is, not in one formation, but as three geographically separate "regimental combat teams."

At the outset of the war on March 20, the three units -- the 1st, 5th and 7th Marines, totaling about 20,000 troops -- drove from Kuwait to seize the Rumaila oil field, which is one of Iraq's most important economic assets, located about 20 miles west of the city of Basra. Then they pushed 75 miles north to Nasiriyah, where they skirmished with Iraqi irregular fighters and crossed the Euphrates River beginning around March 24. They moved into central Iraq and then paused as they grew low on some supplies and a huge sandstorm howled across the country. Earlier this week, the Marine units drove on two axes toward Kut, where Dowdy's 1st Marine Regiment was ordered to pin down the Baghdad Division of the Republican Guard.

Dowdy took command last summer of the 1st Marine Regiment, which is based at Camp Pendleton, Calif. Including units attached to the regiment for combat, he had command of more than 6,000 troops, according to

Before this assignment, he was the assistant chief of staff and chief planner for the 1st Marine Expeditionary Force, which is the umbrella unit for the Marines fighting in Iraq. Born in Little Rock, he graduated from the University of Mississippi and joined the Marines in 1979. His service biography indicates that the current war in Iraq is the first time he has seen combat. During the 1991 Persian Gulf War, in which much of the combat Marine force served, he was the commander of the Marine Corps security unit in Keflavik, Iceland.

"Good man," retired Marine Gen. Richard Neal said of Dowdy, who he said was a student of his years ago at the Amphibious Warfare School at Quantico.

Dowdy's removal puzzled veterans of the Corps, which -- with just about 16,000 officers -- is small enough that many senior Marines come to know each other.

"Jim Mattis was one of my battalion commanders during the first Gulf War," said retired Marine Gen. Carlton Fulford. "I have great confidence in his judgment. I know of Joe Dowdy by reputation, but not personally. He has a fine reputation."

The key to the situation, some officers suggested, is likely Mattis's views on how forcefully a unit should act in combat. "Jim Mattis is a very aggressive commander -- we wouldn't want it any other way," said retired Marine Lt. Gen. Jack Klimp.

In any case, said Fulford, removing a commander in combat is an extraordinary move that isn't taken lightly. He recalled that during the 1991 Gulf War, when he commanded the 7th Marines, and when Mattis commanded one of his battalions, he decided to remove another of his battalion commanders.

"It was one of the most difficult decisions I ever made as a commander," he recalled. But, he added: "In the final analysis, I believed the commander was not prepared to lead his men into combat, and that was the most important issue."

Col. Joe W. Dowdy has been removed as commander of the 1st Marine Regiment, which is engaged in combat in Iraq.