The U.S. Department of Defense has found that the current war in Iraq and Afghanistan is causing many troops to leave the service, but not for the reasons you would think. The biggest complaints involve the heavy work load, and the time spent away from families, and time to relax and recuperate. Danger and physical risk is not a major factor. As a practical matter, the losses from the heavy work load are not a major problem, because the reenlistment rate has gone up since the war began. But numbers are not everything, because it's the experienced NCOs and officers getting out that do the damage. Losing experienced leaders makes a big difference, even if you are keeping a larger number of more junior troops.
The violence in the combat zone is something all the troops headed there are keenly aware of. But the troops can do the math, and realize they only have about a three percent chance of getting hurt (from combat, disease, accidents) over there, and only about a tenth of those hurt, will die. Moreover, the casualties are not evenly distributed. As is usually the case, about 20 percent of the troops take 70 percent of the casualties. In other words, for most of the troops, they have about a one percent chance of getting hurt, while the combat troops, and those who are running convoys a lot, have about a ten percent chance of getting hurt. For the combat troops, in an all-volunteer force, they know what they are getting into, and the ten percent casualty rate is not stopping people from joining, or staying in. While no one wants to get killed, getting the Combat Infantry Badge, and a Purple Heart medal if you are wounded, means a lot. For the rest of your life, it tells people that you went the limit. You've been there. But for many of the older, married troops, the strain on the family is more of a factor than is the personal danger.
The American military has concentrated on the impact of stress, in a trend that has been going on for nearly a century. While the stress of combat has been reduced, the stress of operations has increased. Most (over 85 percent) of troops never get exposed to combat, but most of them get involved in heavy workloads. This is causing more losses than combat.