During World War II, the official friendly fire rate was 2-3 percent. But a study later done by the Army, after Vietnam, indicated that the real friendly fire rate during World War II could be as high as 20 percent. The reason for the lower official rate was that it was demoralizing for the troops to ascribe a fellow soldiers death to friendly fire. This was particularly true with bullet wounds, bullets from the weapons of fellow soldiers. Getting hit by your own artillery or aircraft was common in World War II. It was so bad that GIs would call their Air Force the "American Luftwaffe." The problem was that, even during World War II, the US had more firepower than our opponents. And during World War II, fire control was not as precise and accurate as it is now. The friendly fire situation became harder to ignore during the Korean war and Vietnam. Today, with embedded reporters and videocams all over the battlefield, it's almost impossible to ignore friendly fire. There are so few casualties that each one can be examined in sufficient detail to determine if it was friendly fire. For example, the bullets taken from a dead soldier can easily be identified as enemy or friendly. And with a little more effort, even shell fragments can be so identified. On the positive side, the opportunities for friendly fire are probably lower today than ever before, because of better fire control and communications. But the ratio of friendly to enemy firepower is greater than ever. So American soldiers are exposed to far more friendly firepower on the battlefield. And any soldier who's been there will tell you that combat is a very confused situation. It's easy to hit one of your own guys, especially in forests or urban areas.