military planners in Baghdad have devised a simple formula -- what one general called a "rough rule of thumb."
The formula estimates that for every three Iraqi battalions and one Iraqi brigade headquarters achieving a readiness rating of level two, a U.S. battalion can be dropped....
The withdrawal formula is a planning tool, several officers stressed, not a definitive predictor of how many U.S. forces are likely to leave when. (emphasis mine)
So in 2005, the US was basically assuming that a US unit could be replaced by an Iraqi unit at a single higher echelon of command; an Iraqi battalion would replace a US company, an Iraqi brigade would replace a US battalion, and an Iraqi division could supplant a US brigade.
I think it is safe to assess British military forces as near equivilants in terms of combat power and effectiveness as US forces. They have a little less armor and air power attached to them, but they also have a great reputation for being better infantry than US formations. This reputation is built on both experience and a great deal of long term career professionalism that encourages institutional knowledge at the company and battalion level.
I mention all of this because one of the articles covering the fighting in Karbala that Cernig mentioned today had an interesting nugget concerning my post on Basra and US supply lines. From the AP:
On Tuesday, Hakim al-Miyahi, head of the security committee of the Basra municipal council, told The Associated Press that Iraqi forces were incapable of maintaining order in the city once the British leave and that the Baghdad government should send reinforcements.
"Some disorder will occur in the absence of British troops in Basra," he said. "It will take at least two army divisions to fill the gap that will be created by British troop withdrawal." [emphasis mine]
The British have a reinforced brigade in Basra province, and a reinforced battalion within the city. Most of the rest of the force is based at the airport, and the battalion is begining to pull out within weeks. The British have roughly four combat battalion equivilants in theatre as of July 1, 2007. So going back to the 2005 estimate that Iraqi units one echelon of command higher could supplant US units, and with the assumption that a US unit is equivilant to a UK unit, we would predict that the security backfill would be four Iraqi Army brigades. Instead, at least six are being called to maintain a security equilibrium that is not that good.
Combine this with the projected deployment of a US brigade to Basra, and we get a pretty damning indictment of the capabilities of the Iraqi government security forces. The US brigade probably is a two battalion force, so six Iraqi brigades are the effective replacement for two British battalions. Each British battalion is now considered the equivilant of an Iraqi Army division. So now an Iraqi Army unit is considered to be only 33% as capable as the US was projecting it to have been two years ago.
Okay now for tea-leaf reading and pure speculation. I am guessing that al-Miyahi is probably a Fadillah supporter due to his position on the security committee, as Basra is currently governed by Fadillah. Basra is in the middle of a three way fight between SIIC/ISIC, Sadrists/JAM, and Fadillah over who controls the oil, the money and the corruption. The Iraqi Army is locally raised for half their divisions, and from what all of the rumint is saying, the Sadrist JAM has the best infilitration in the Iraqi Army. So is Fadillah trying to bring in another big militia on their side of a mutual co-belligerence against SIIC? I need better tea leaf readers than me at this point....