Falluja

The US/Iraqi assault on Falluja has begun. What I can't quite figure out is how many insurgents they expect to actually stay in the city. Keep in mind the insurgents have been fighting a guerilla terror campaign where they bomb a target, often civilians, and then melt back into the general populace. It's very hard to tell insurgents from civilians. Also they've estimated that up to half of Falluja's 300,000 people have already fled the city. Now if you were a terrorist bastard who likes to disappear into the civilian population between attacks, would you be staying in Falluja, knowing for weeks that the US military is preparing to assault the city? Oh, some diehards will, but I'd certainly bet that many of them have already left and will continue to leave in the coming days, looking exactly the same as all the other civilians fleeing the city.