Two suicide bombers blew themselves up today among a crowd of Shia pilgrims headed for Karbala, and 93 more Iraqis were killed. All of this gives the impression that Iraq is in the middle of a religious war. Some pundits have even suggested that the Shia and the Sunni have been fighting for centuries, this fighting will continue into the indefinite future, and America should not be in the middle of this but should get out of Iraq sooner rather than later.

But the Shia and the Sunni have not been fighting for centuries. In fact, for most of Muslim history they have not been fighting at all. Two decades ago Shia and Sunni Muslims were shoulder-to-shoulder in the trenches, laboring together to drive the Soviet Union out of Afghanistan. Even in Iraq, the clashes between the Sunni and the Shia are not based on religion.

So why are they fighting?

The short answer is that you need a mafia to do it. You need a group of henchmen numbering in the thousands who will run every department of government, not to mention every school and post office and bank. And where do you find such men? You go to your home town of Tikrit, and recruit among your own tribe, which happens to be Sunni.

So the Sunni Baathists ruled Iraq for more than two decades, and now they have been pushed out, not only because of the ouster of Saddam but also because of de-Baathification. And the other guys, the Shia majority, are now running the country thanks to democracy. The Sunnis who have lost their jobs and authority are drawn to the insurgency, and there is a battle between the two groups for who is going to rule Iraq. It's a battle over power, not religion, and it's not going to go on indefinitely: chances are one side will win.

The question for America is whether we are going to back the winning side, in which case there will most likely be a pro-American government in Iraq, or whether we are going to get out, in which case there will almost certainly be an anti-American government, no matter who wins the tribal conflict.

The insurgents are setting fire to mosques and attacking pilgrims for the simple reason that they know this is the best way to inflame passions, and stoke the flames of confusion and conflict. Chaos is their best hope for chasing the Americans away, and for enabling the alliance of Al Qaeda and dethroned Baathists to seize power.