As best I can tell, nobody can quite figure out what's happening in Iraq right now -- nobody sure who did what that led to the current fighting or exactly who's fighting whom. Thus we get reporting about how the fighting "threatened to destabilize a long-term truce that had helped reduce the level of violence in the five-year-old Iraq war." Once a giant battle is already under way it seems a bit late to worr that a cease-fire might be threatened, but that's a sign of how confused the situation is.

The International Crisis Group's old report on Shiite politics in Iraq remains a vital backgrounder if you're interested.