March 24, 2007: The U.S. Army has been studying combat fatigue (or PTSD, post-traumatic stress disorder) a lot more these days. Currently, about 400 soldiers a year are sent home from Iraq because of severe PTSD, and thousands have less serious bouts of PTSD, which are treated in Iraq, with the soldier soon returning to duty.

What the army is up against is something they discovered during World War II. Back then, PTSD was called combat fatigue, and it was a serious problem. In the European Theater, 25 percent of all casualties were serious PTSD cases. In the Pacific Theater, the rate varied widely, depending on the campaign. In some of the most intense fighting, like Okinawa in 1945, it accounted for over a third of all wounded.

The statisticians examined all those medical records and discovered that few soldiers went more than 200 days in combat without suffering a severe case of combat fatigue. Actually, the number of days a soldier could survive in combat, before feeling the effects of PTSD varied from 100-200. There were exceptions, as PTSD vulnerability, like everything else, occurred according to a bell-shaped curve. There were some troops who had severe anxiety attacks, and other PTSD symptoms after only a week or two of combat. On the other extreme, there were men who never seemed to suffer any PTSD symptoms. It was later discovered that, as with most things, genetics and brain chemistry played a large part in the ability of some people to be virtually immune to PTSD. But there's still no PTSD vaccination, and lots of PTSD victims.

PTSD was less of a problem during Korea and Vietnam, because troops usually served only one 13 months tour in the combat zone. It was for the Korean War that the "12 month tour of duty" was invented (to spread the pain around, otherwise a smaller number of troops would have stayed there, "for the duration.") But Iraq is different. The lower casualty rates have meant that a lot of troops are going back for multiple tours of duty. Thus, the army and marines are now faced a large number of troops hitting the 200 days of combat "wall". Based on past experience, that should mean more cases of serious combat fatigue. That results in troops dangerous to themselves and those around them.

In Iraq and Afghanistan, the army has found ways to delay the onset of PTSD by providing better living conditions, and equipment that makes combat less dangerous. The army also provides some leave time during the tour, which allows the soldiers some time outside of Iraq, and even a visit with his family back home. This has delayed hitting the wall, not eliminated it. Troops may be able to handle 300, or more, days of combat. But many troops are sensing that they are approaching the wall, and transferring out of combat jobs, or not reenlisting. The numbers are not great, but it is a trend. You cannot ignore the long term impact of combat fatigue.