The Pentagon is split on troop drawdown in Iraq, but the split has nothing whatsoever to do with politics or non-military stateside considerations.

Discussions about a possible pause in troop cuts in Iraq underscore what is shaping up as a sharp debate between the U.S. commanders running the war and those who have to provide the forces for the fight.

Military leaders, including Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, stressed Friday that it is too soon to tell if troop withdrawals should slow or stop. But they acknowledged that it is becoming more and more difficult to find the Army soldiers and Marines to send to battle in Iraq and Afghanistan.

“The question becomes not so much a pause,” said Marine Commandant Gen. James Conway Friday, “but how much risk is a commander willing to accept” when weighing the conflicting needs of providing troops for war while still giving some relief to the over-stressed force.

Summary of force size in Iraq since the inception of Operation Iraqi Freedom – 2003: U.S. forces were at 143,000 when Baghdad fell in April and ranged from a high of 148,900 in June to a low of 121,100 in December.  2004: Ranged from low of 108,900 in January to high of 150,200 in December.  2005: Started in January at peak of 159,000 and ranged from low of 138,000 from June through August, then back up to 157,000 in October.  2006: Ranged from 137,000 in January to low of 125,000 in June to high of 147,700 in October.  The graph depicts force size in Iraq from January of 2007 through January of 2208, with the data from January 2008 to July 2008 being interpolated based on an unofficial goal expressed by Defense Secretary Robert Gates of 100 000 by December of 2008.

The split in thinking is not general, but very targeted and pertinent to specific units and lengths of deployment.

The debate in the Pentagon is over what to do when those five brigades are brought home in coming months. It is complicated by the mixed picture in Iraq, where violence levels are far lower than a year ago but have shown signs of worsening in recent days, especially in volatile areas north of Baghdad.

Defense Secretary Robert Gates has said he hopes conditions in Iraq allow a cutback to 10 brigades by year’s end. That would make it possible for the Army to reduce combat tours from 15 months to 12 months.

I feel that there are two aspects of this analysis, one flawed and the other “spot on.”  First, the lengths of deployment are terribly long and wear thin for both the warriors and their families.  The size of the Army and Marines should have been grown with haste four years ago.  The force size in Iraq during calendar years 2003 – 2006 reflects the Rumsfeld – Wolfowitz model, which, although obviously wrongheaded, was in part based on the size of the Army and Marines at the time (along with a naive belief in the healing powers of democracy).  The size of the armed forces has not grown substantially since then, and so the only way to accomplish the “surge” was to lengthen deployments.  The Pentagon is right to worry about an Army and Marines that are stretched too thin to continue constant and lengthy deployments.

However, the draw-down of troops will not be highly dependent on individual and specific acts of terrorism, but rather, sweeping strategic assessments of regions and factions.  For instance, al Qaeda is essentially defeated in Iraq (with some operations still ongoing in the North), and is redeploying to other areas of the globe (as we predicted in November of 2007).  However, there is pressure from within the Mahdi army for Moqtada al Sadr not to renew his commitment to a truce when it expires this month (note that a failure to renew the truce would likely affect Shi’a on Shi’a violence more than Shi’a on Sunni violence).  There are important developments that must be monitored before final decisions can be made to draw down to a mission of national security and ensuring sovereignty versus regular constabulary operations.