One of the looming problems in Iraq is combat fatigue. A problem that didn't become fully recognized until the 20th century, it's often difficult to know when troops have been stressed out by combat. Combat fatigue has been around for a long time, and became a major problem in the 20th century, because so many men were exposed to so much firepower and stress for such extended periods. Typically, a man suffering from combat fatigue lost interest in his surroundings, acted distracted and dispirited and got sloppy in his work. Often, such men quickly became casualties of enemy weapons. If you are not really careful in a combat zone, you are likely to get hurt quickly.
Experience in World War II, and other wars since then, has produced some rules of thumb. For example, 30 days of intense combat will produce a 25 percent increase in casualties because of combat fatigue. The additional casualties are men suffering from combat fatigue. However, unconventional warfare will produce 33-50 percent more casualties. Again, all the extra losses are combat fatigue. Israel saw this happen during its last sustained war, the 1982 invasion of Lebanon. Many of the other wars in the period, like the Iran-Iraq war and Russian operations in Afghanistan, produced predictably high numbers of combat fatigue casualties.
The United States was slow to understand what combat fatigue was, and how best to deal with it. During World War II, the British and Germans developed much better techniques for dealing with "burned out" combat troops. You can see some of those techniques being used by American commanders in Iraq right now.
For example, during World War II, if was found that when troops start to get a little flaky, or flip out, take them to a rest area just behind the front lines. Clean them up and let them get some rest. Have chaplains or specially selected combat veterans (usually older NCOs) available to talk to the combat fatigue sufferers and help calm them down. One thing combat fatigue victims get upset about is "letting their buddies down." Most of them do what to get back to their combat unit, which becomes something of a family for men in battle. But you can't send them back when they are mentally disordered and dangerous to themselves and their friends in a combat zone.
In Iraq, the policy is to send combat troops to rest areas in Iraq. This is usually one of Saddam's many palaces, which are usually well equipped (swimming pool, well maintained grounds, comfortable rooms) for relaxation. There are other rest areas in Kuwait and other Gulf States (but not Saudi Arabia.) It's also been announced that troops will be given two weeks of home leave in the middle of their one year Iraqi tour of duty.
If the leave policy is applied in time, and officers and NCOs keep a careful watch for the signs of combat fatigue, the vast majority of troops will not be at risk of falling into the apathy and depression that generally characterizes combat fatigue.