A moat around Baghdad

I didn't quite understand it when Bush said in his news conference that they were building a "berm" around Baghdad until I saw this:

BAGHDAD, Iraq - Iraqi security forces will dig trenches around Baghdad and set up checkpoints along all roads leading into the city to try to reduce some of the violence plaguing the capital, the Interior Ministry said Friday.

Does this mean they're going to give the rest of the country to the insurgents? It's going to end up like Afghanistan, with the government controlling only Kabul/Baghdad. Maybe not even that, since al Sadr controls more than half of the population of Baghdad.

Didn't moats go out with castles as a means of defense? When I said in an earlier piece that Bush and the Pope were trying to take us back to the days of the Spanish Inquisition, I didn't literally mean going back to the defensive strategies they used in those days. I guess I was more prescient than I thought.