addrzejpw, I think that's the question of the hour. The only real opposition groups in Iraq are the various parties of the Iraqi National Congress, most (all?) of which are Kurdish and state that one of their goals is the establishment of a independent Kurdish state. That sure as hell ain't gonna happen -- Turkey, a NATO member, would be scared ****less.
I think it's been estimated that the Iraqi National Congress could field an army of up to about 40,000 men. Saddam has about 375,000 regulars and over 650,000 more reserves, so this wouldn't be a Northern Alliance v. Taliban type of war. The US would have to commit a significant force. If the US does most of the fighting, it'd be a good excuse not to give the IRN what they want ... we'd probably see some sort of East Timor-esque UN operation to set up a new government.
kerelybonto