Journalists in combat pools were assigned to the First Infantry during the breaching operation, but none of their reports mentioned the live burials. In fact, the reports noted that few slain Iraqis had been visible in the bunkers and trenches.

The Pentagon has provided no official estimate of Iraq's overall casualties. The Defense Intelligence Agency issued a heavily qualified analysis in June estimating that 100,000 Iraqis had been killed and 300,000 wounded in the war but said the figures had a 50 percent margin of error.

Breaching operations are among the most dangerous maneuvers for ground troops. Obstacles like minefields and barbed wire can slow advancing forces, leaving them particularly vulnerable to enemy attack.

Colonel Maggart said two the First Infantry units had punched 16 tank-width lanes in the Iraqi defenses.

In most cases M1-A1 Abrams tanks mounted with a plow were positioned on either side of and parallel to the Iraqi trenches, the colonel said. The ditches were typically several hundred yards long, three feet wide and four feet deep. Operating like snowplows, the tanks drove alongside the ditches, filling them in. Colonel Maggart said that in most cases, Iraqi troops had enough time to see the plows coming, jump out of the trenches and surrender. Gunners Beside Plow Tanks

For those Iraqi soldiers who continued to resist from outside the trenches, Bradley fighting vehicles equipped with heavy machine guns and 25-millimeter cannon drove alongside the plow tanks, Colonel Maggart said.

"The Iraqi soldiers that were killed in this process were those that chose to stay in their trenches or behind obstacles and fight during the breaching operation," Mr. Williams said. But neither Colonel Maggart nor Mr. Williams said how they could be sure that wounded Iraqi soldiers had been able to get out of the trenches in time.