According to the British Observer, it has already begun:
The battle between Sunni and Shia Muslims for control of Baghdad has already started, say Iraqi political leaders who predict fierce street fighting will break out as each community takes over districts in which it is strongest.
"The fighting will only stop when a new balance of power has emerged," Fuad Hussein, the chief of staff of Massoud Barzani, the Kurdish leader, said. "Sunni and Shia will each take control of their own area." He said sectarian cleansing had already begun.
Many Iraqi leaders now believe that civil war is inevitable but it will be confined, at least at first, to the capital and surrounding provinces where the population is mixed. "The real battle will be the battle for Baghdad where the Shia have increasing control," said one senior official who did not want his name published. "The army will disintegrate in the first moments of the war because the soldiers are loyal to the Shia, Sunni or Kurdish communities and not to the government." He expected the Americans to stay largely on the sidelines.
Iraqi officials and ministers are increasingly in despair at the failure to put together an effective administration in Baghdad. A senior Arab minister, who asked not to be named, said: "The government could end up being only a few buildings in the Green Zone."
The mood among Iraqi leaders, both Arabs and Kurds, is far gloomier in private than the public declarations of the US and British governments. The US President George W Bush called this week for a national unity government in Iraq but Iraqi observers do not expect this to be any more effective than the present government of Prime Minister Ibrahim al-Jaafari. One said this week: "The real problem is that the Shia and Sunni hate each other and not that we haven't been able to form a government."
The Shia and Sunni hate each other over there and the wingnuts and moonbats hate each other over here. So it goes. And I'm not repeating what I always say: that anyone with any knowledge of the history of Iraq could have predicted this outcome. But such people don't get government jobs in the U.S..