Time to Leave
I would have called it a civil war a long time ago, but if this level of violence continues (it will), and if the government collapses (it probably will sooner or later), then it's definitely a civil war. The Pentagon's claim that it is not already a civil war must be based on some very technical definition of the term "civil war." For example, that it's not a civil war until an officially recognized regional government entity formally declares independence, raises an army, meets the army of the national government on the battlefield and engages in conventional warfare. That's how our civil war happened. That isn't how most civil wars of the 20th century happened.
Civil wars reflect the societies that wage them. The American Civil War reflected the antagonism among elements of 19th century American society, and the Mason-Dixon line, the geographic and cultural fracture along which the two sides split, was a feature of existing devisions.
The bloodshed in Iraq reflects the divisions in Iraqi society; what is happening now is exactly what skeptics of the invasion warned us would happen. As you may recall, it was theorized that the only thing holding Iraq together was the universal fear of Saddam Hussein. It was his regime alone, and not any sense of national identity, that held the country together. Removing Saddam from power would be like removing the iron hoops from a barrel under pressure; with nothing holding the staves together, the barrel would blow apart. This was the conventional wisdom from the end of the Gulf War until Colin Powell's infamous presentation to the U.N. Now, we can turn on the news any day and see that it was right on the money.
This war is our fault, but we are not serving and can not serve any meaningful positive role in the country now that these events are in motion. The only humane thing we can do for Iraq is pack up our things and leave, and promise to never, ever come back. We have been fucking with the Middle East for too long.