A year ago, before U.S. troops entered Baghdad, military observers (including this one) were predicting a drawn-out, bloody mess. Urban war zones, they warned, would blunt America's technology edge -- radios don't work so well in concrete canyons, and unmanned spy planes can't see inside buildings. More importantly, perhaps, Iraqi fighters could easily pop in and out of a city -- and a civilian population -- they knew a thousand times better than any G.I.

But then: nothing. Saddam's forces vanished. American soldiers were left to deal with a nasty pirhana of an insurgency. But it was nothing like the street-to-street combat so many had forecasted.

Until now, it seems. 12 Marines were killed yesterday fighting Sunni insurgents -- likely former Saddamists -- in "nonstop, house-to- house, roof-to-roof fighting" in Ramadi, near Baghdad. Another group, from the Marines' 2nd battalion, 1st regiment, fought "block-to-block" in Fallujah, according to the AP. In a half-dozen other cities across Iraq, Shi'ite forces aligned with the radical cleric Muqtada al-Sadr are battling with U.S. and allied troops. Sadr now appears to be in control of Najaf, a city of 500,000 that's one of the most holy in the Shi'ite faith.

It's clear from reports like this that Sadr's militia wouldn't pose a hint of a threat to allied troops -- if this was open combat, traditional war. But it's not.

The Command Post has ongoing updates. And Phil Carter's blog is a must-read in these times.