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Pentagon plans for an Iraqi civil war

Pentagon and military officials say Iraq's not fighting a civil war yet, but warn that Iraqi security forces and the government could still collapse, dragging the country into one. So the U.S. military is drafting a series of contingency plans to deal with that very ominous possibility.

Military officials tell NBC News the first objective, however, is to head off a civil war. The U.S. military hopes to keep Iraqi security forces from taking sides in the sectarian violence by pressuring the Iraqi government to crack down on any rogue elements within the police or military.

The second option: U.S. forces could again be sent into combat against sectarian militias, which military officials say would require an increase in the number of American soldiers and Marines in Iraq.

And the last resort, if violence is spinning out of countrol: Military officials say they would also have to consider the possible withdrawal of American forces.

But why, after three years in Iraq, is the U.S. military still bogged down in the war?

Gen. William Wallace, the top military commander for the U.S. invasion of Iraq, blames it on a series of miscalculations from the start.

"I do fault myself and others for not questioning, perhaps, or challenging some of the assumptions that were made," says Wallace.

Lt. Gen. David Petraeus, who led the 101st Airborne in Iraq, now heads the Army's training center at Fort Leavenworth, Kan., teaching the lessons learned from the war. One of those lessons is that the U.S. military stormed into Iraq with little knowledge of Iraqi culture, which is now being taught in all U.S. combat training.

"We don't speak the language, the dialect," says Petraeus. "We have to work through interpreters. We are different. We are from a different culture.'

U.S. commanders had also failed to recognize the potential threat from insurgents.

But for nearly two years the military was battling the insurgents based on Army doctrine for counter-insurgencies that was 20 years old. It's since been rewritten.

But ultimately, Petraeus says the insurgents can not be defeated by the military alone — that the Iraqis must establish a legitimate government.

"I think the Iraqi leaders recognize that that is an imperative," says Petraeus. "They must, in fact, come up with a government of national unity."

Without that, Petraeus warns it could be a long, hot and potentially bloody summer.