Helena Cobban: Is This What the Current Fighting in Basra Is About?. Looks like the US is building one of its huge enduring but not exactly permanent military bases near Basra, an area they've mostly left to the British until lately (e.g., as the Brits are leaving). They will need some kind of force presence to protect vital supply lines from Kuwait, and having the whole region largely controlled by the Mehdi Army evidently doesn't give them much of a comfort level.

Late breaking news is that Sadr has pulled his fighters back in a deal that was brokered in (if not necessarily by) Iran. It looks as though Maliki, at least, has realized his miscalculation. I doubt that anyone in the US chain of command has learned much, so this is likely nowhere near the end of the story.