How could the U.S. Army have a troops shortage in Iraq when they have over a million troops available? First, while the U.S. Army has 1.2 million troops, only half a million of those are active duty. The rest are reserve and National Guard units (together, commonly called "the reserves."). The last major reorganization of this force was in the 1980s, when the Total Force concept was implemented. Total Force meant that the army could not get into a major war without mobilizing several hundred thousand reserve and National Guard troops. This was because many of the support units (everything from civil affairs to specialized engineer units that can operate ports overseas) were moved into the reserves. Most of the active duty units were combat units, who required specialized training you didnt find in the civilian economy (infantrymen and tank crews, for example),. Many of the reserve and National Guard troops had military jobs similar to their civilian ones (engineers, medical, computer related, administrative.) The Total Force was a good idea if you planned on fighting a major conventional war. But little wars like Afghanistan and Iraq were a different matter. For example, Iraq required lots of MPs (Military Police), and most of these were in the reserves. But there were a lot of troops in the reserves who had skills that were not needed in Iraq, or Afghanistan, or the Balkans. In fact, some 58 percent of the reserve and National Guard troops have not been mobilized in the last ten years. Thats because the reserves are still organized for major Cold War campaigns that are not likely to happen.
The Iraq campaign also demonstrated that having to call up reserve and National Guard units slowed things down, as those units require weeks, and sometimes months, to get ready to move overseas. Because of this, some of the key support units will be moved back to the active duty force, making it easier to get units on their way to an overseas battle zone while the reserve units are made ready for action.
Another aspect of the reorganization is to force reserve and National Guard units to be more ready to go on active duty. The National Guard, in particular, has lots of troops tied up in undermanned units that have neither the troops nor the training to go on active duty. This is because the National Guard, in peacetime, belongs to the states. These units are the direct descendents of the ancient state militias. Some units have been around for centuries. But as population patterns shift, there are no longer enough locals to recruit from. No state politician wants to risk losing votes by moving or disbanding the unit, and even if the army gets federal permission to shuffle things around, there is still a political cost as the states congressional delegation gets involved. The states are not much bothered by the undermanned units, because all they use the troops for are emergencies. In those cases the National Guard is using its trucks to move things, its troops to guard things and its armories to provide shelter for civilians fleeing some natural disaster. None of these duties require a great deal of readiness for mobilization and combat duty.
While there are many fully manned and combat ready units in the National Guard, its a pretty random event. If the conditions are right (enough population to recruit from, a state willing to get behind and support recruiting, good officers and NCOs), youll get a good unit. But too often, the conditions are not right. Getting this fixed has proved impossible so far. But you can reorganize the National Guard forces and find units that are up to whatever current tasks the active duty forces are assigned to.