US forces dropped a pair of 2,000-pound bombs early yesterday morning on a bunker complex believed to be an insurgent training facility on the southern edge of this city, where the most dedicated and best trained rebel fighters are making a last stand.
The bombs shook the ground of the former insurgent stronghold and set off secondary explosions that went on for 45 minutes but could not be seen above ground, persuading officers of the Army's First Infantry Division that there were large stockpiles of weapons underground.
After nearly a week of fighting, American forces said they and their Iraqi counterparts had wrested most of the devastated city from insurgents, but continued to comb through buildings in search of an elusive enemy and to unleash heavy artillery that added to the destruction that Iraq's US-backed government will have to repair.
''It's like a drop of mercury in a maze," US Marines Major General Richard Natonski, the architect of the Fallujah operation, said yesterday of the difficulty capturing small groups of insurgents roaming the city.
''You push it in one direction and it breaks into pieces and flows all around," Natonski said on a visit to a forward command post.
Yesterday, Natonski said the operation was a success -- despite the eruption of violence in Mosul and other parts of the Sunni triangle -- because now it would not be easy for insurgents to establish a new base like the one they had in Fallujah.
''When they're moving they're vulnerable," he said. ''They no longer have the sanctuary they used to have in Fallujah, where they could rest, refit, resupply, and go back out."
The insurgency had also lost an important symbol, he said.
''This was there in your face: 'We have Fallujah and you don't.' They can't say that anymore," Natonski said.