"All of us were a bit taken aback by the complete destruction of the Iraqi army and the near total dissolution of Iraqi security institutions, especially police," said Abizaid, who took over from General Tommy Franks, who headed the Central Command before and during the war.

Abizaid also acknowledged that US troops remaining in Iraq while interim leaders try to set up a new government in Baghdad were facing guerrilla tactics.

"We're seeing a cellular organization of six to eight people armed with (rocket propelled grenades), machine guns, etc., attacking us at some times and places of their choosing and other times we attack them at times and places of our choosing," said Abizaid.

"I think describing it as guerrilla tactics being employed against us is ... proper ... in strictly military terms."

The Third Infantry Division was unexpectedly ordered Tuesday to remain in place, its return to the United States postponed due to the state of insecurity in Iraq.

Everyone had hoped for their return "relatively soon", along with troops from the First Marine Division "provided certain expectations were ... met on the security front," Abizaid said.

"Once we started to understand that environment, we knew that we were going to have to extend people longer than we had hoped."

He stressed the decision to remain was a tactical one and was not being forced on the US military.

"War is a struggle of wills," he said. "They are not driving us out of anywhere."

WAR.WIRE