How stretched are they? A Congressional Budget Office report issued in October 2005 noted that overall the total level of land forces deployed to Iraq and Afghanistan has averaged about 175,000 to 200,000 personnel over the past two years. Those levels of force are well above what CBO considers sustainable over the long term.

For example, as of January 2006, nearly all of the available combat units in the U.S. Army, Army National Guard, and Marine Corps have been used in current operations. Every available combat brigade from the active duty Army has already been to Afghanistan or Iraq at least once for a 12 month tour. Many are now in their second or third tours of duty. Approximately 95 percent of the Army National Guard's combat battalions and special operations units have been mobilized since Sept. 11, 2001.

Short of full mobilization or a new presidential declaration of national emergency, there is little available combat capacity remaining in the Army National Guard. All active duty Marine Corps units are being used on a "tight" rotation schedule -- seven months deployed, less than a year home to reset, and then another seven months deployed -- and all of its Reserve combat units have been mobilized.

Senior Army and Marine Corps officers have been warning for some time now that without a troop reduction in Iraq, the present schedule of combat tours would be difficult to sustain without an increase in the number of forces. The concerns had reached such a level that top Army leaders broached the issue of changing deployment rules to allow for more frequent call-ups of National Guard and Reserve units to relieve pressure on the active duty Army.

But because the Army relied heavily on the Guard and Reserve early in the war, many units have hit legal deployment limits, which allow for two years overseas out of every five. Without a change in those rules to allow more frequent Guard deployments, the Army would be forced to consider a push for an expansion of its active duty force, which now stands at 504,000.

Restrictions on the use of the Guard are a matter of interpretation. Guard officials said that under President Bush's current mobilization order, its members may not be called up if they have served for 24 consecutive months. But a conflicting U.S. Department of Defense policy interprets the order as limiting the call-up of those who have tallied 24 months of total service, regardless of the length of time served consecutively. That view would put more Guard members off-limits for remobilization without a new order from the president.

Even if the readiness problem could be solved by spending more money on it there would still be a larger problem. Previously, military and Pentagon officials hinted that they hoped U.S. troop deployments in Iraq would drop to 100,000 by the end of 2006. But now, with the surge, the plan is to increase troop levels to roughly 150,000 troops on the ground.

However, it is not possible to keep 135,000 troops deployed in Iraq, or anywhere else, indefinitely. The ones in Iraq and elsewhere must eventually be relieved by fresh troops, since excessively long or too frequent periods of time away from home creates the risk that soldiers will decide against a military career.

For a professional volunteer military force to be able to retain soldiers over time, the rule of thumb for active duty units is a three to one rotation ratio, meaning three units are needed to keep one unit fielded. So keeping 150,000 troops in Iraq requires an additional 300,000 for rotation or a total of 450,000 soldiers.

This number is precariously close to the total size of the active duty Army, about 500,000 troops. Moreover, the U.S. Army has another 64,000 troops deployed elsewhere overseas that requires a total of 192,000 troops to sustain it. So when you do the math, the Army is about 142,000 soldiers shy of being able to keep up the current deployments.

(David Isenberg is a a senior research analyst at the British American Security Council and a research fellow at the Independent Institute. He is also a member of the Coalition for a Realistic Foreign Policy and an advisor to the Straus Military Reform Project of the Center for Defense Improvement, Washington, D.C. These articles are derived from my study "Budgeting for Empire" just published by the Independent Institute.)

(United Press International's "Outside View" commentaries are written by outside contributors who specialize in a variety of important issues. The views expressed do not necessarily reflect those of United Press International. In the interests of creating an open forum, original submissions are invited.)

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