Who are at the Iraqi insurgents, and why are they fighting?

The Mystery of the Insurgency - New York Times

The insurgents in Iraq are showing little interest in winning hearts and minds among the majority of Iraqis, in building international legitimacy, or in articulating a governing program or even a unified ideology or cause beyond expelling the Americans. They have put forward no single charismatic leader, developed no alternative government or political wing, displayed no intention of amassing territory to govern now.

The best guesses seem to be that the anti-occupation and anti-government forces are a mixture of millenialist terrorists, straight out simple criminals, Baathist loyalists, Sunni racists, and, maybe, a nationalist agenda.

Compared to other insurgencies, the nationalist theme seems the weakest.

The 'incoherence' doesn't mean the Iraqi goverment and people, and the US, will win. It may be that the insurgents are quite willing to destroy Iraq in order to further their own agenda. Destroying Iraq seems doable.