Why we can't send more troops to Iraq.

As we're often told, 1 million men and women serve in the U.S. Army. So, why is it such a strain to keep a mere 150,000 in Iraq? What are the other 850,000 doing? Why can't some of them be sent there, too? And if they really can't be spared from their current tasks, what broader inferences can be drawn about America's military policy? Should we bring back the draft to provide more boots on the ground—or, alternatively, scale back our global ambitions so fewer boots will be needed?

First, let's look at those million soldiers. Who are they? The Web site GlobalSecurity.org has a pie chart breaking them down into categories. It turns out that fewer than 40 percent of them—391,460—are combat soldiers. And fewer than 40 percent of those combat soldiers—149,406—are members of the active armed forces. (The rest are in the National Guard and Army Reserve.)

The others are support and logistics troops—50,252 in transportation, 37,763 in medical, 34,270 in the training and doctrine command, and so forth. The distinctions are not ironclad. Transportation soldiers, for example, get shot at and shoot back. Still, however you define it, a strikingly small percentage of the million-man Army consists of active soldiers whose principal job is to fight.

These combat soldiers are organized into brigades (between 3,000 and 4,000 in each). The Army now has 37 active combat brigades—10 in Iraq, one in South Korea (another one, which used to be there, is now among the 10 in Iraq), and one in Afghanistan. That's 12 brigades deployed to hot spots. What about the other 25?

• Nine have recently returned from Iraq or Afghanistan (the rule is 12 months out, 12 months back home—though some units have seen their overseas tours stretched);
• 15 are in training;
• one is reconstituting around the new Stryker combat vehicle.

It would be possible to put a few more of these brigades on the battlefield. Soldiers could be given less training and be allowed less time at their home bases. But the chiefs know that if they did that, they would soon have a disgruntled, ill-prepared Army—and a smaller Army, too, since such strains would torpedo recruitment and re-enlistment rates, which even now are falling well below target. (Soldiers and civilians might feel differently if the war in Iraq were truly a war of national survival or a titanic struggle of civilizations. During World War II, after all, millions were perfunctorily trained before shipping out to Europe or the Pacific, and they stayed there for years until the fighting was over. But the stakes of the present war are far less momentous.)

The fact is, the U.S. Army has substantially shrunk since the Cold War ended 15 years ago—to the point where it simply cannot fulfill the Bush administration's global dreams.

The Army is making some adjustments to fill the gap—mainly by restructuring its brigades so that each one has more combat troops and fewer support-and-service personnel. This process has been going on for a couple of years now. Once the process is complete, the Army will have 43 or possibly 48 combat brigades (in 2000, it had 33)—each brigade smaller but loaded with 20 percent to 30 percent more fighting power. (For more on this, click here.)

With this reorganization, the Army will be able to maintain its current level of troops in Iraq without having to rely so heavily on the Guard and Reserve. (According to an Army spokesman, the last time U.S. troops rotated into Iraq, they consisted of 10 brigades from the active Army and seven brigades from the reserves. The next rotation, later this year, will consist of 15 active brigades and just two from the reserves.)

John Pike, director of globalsecurity.org, describes the result of the restructuring this way: "We'll be able to fight the war we're fighting, indefinitely."