In war soldiers shoot pieces of metal at supersonic speed at one another, and the
human body is not terribly resistant to such things. Their
artillery lobs
bombs which explode far out of sight of the men operating the
cannon. An
Infantryman carries several personal
bombs. We launch
rockets at each other, fire missiles, supersonic slugs of
depleted uranium, metals and fluids that
burn on contact and we have even filled the air with
poison during man's never ending quest for
power. We kill each other in war. Sometimes one side kills people on their own side. There are two reasons for this.
Fragging is what happens when soldiers get rid of an incompetent or distrusted superior. It is always deliberate. But when soldiers kill a friend accidentally it is called
Friendly Fire.
The biggest simple cause of friendly fire is the simple yet sad truth that survival in combat often depends on doing unto the other guy before he can do unto you. More simply put, he who shoots first is the most likely to survive. This means that soldiers are under tremendous pressure to make quick, accurate decisions. The battlefield is not like a chessboard-- commanders rarely find themselves with a complete and accurate picture of where everyone is on both sides. Reports come from everywhere, and some are mistaken. Soldiers, particularly when inexperienced, exaggerate. Soldiers are scared because they quickly learn that real wounds aren't like the kind you see on television. The wounded scream constantly, they beg, and body parts don't stay neatly tucked inside pristine skin. Bombs going off nearby deafen you. The enemy is often invisible, seen only by the flashes of his guns. He doesn't want to be seen, because he knows that being seen will kill him. And so soldiers shoot at where they think the enemy is. Sometimes they get it wrong.
All armies seek to avoid losing people to friendly fire. The best way to avoid friendly fire is through intensive training and the careful adherence to fire control procedures. Train your people to have a real target before firing (this also conserves ammunition which must be carried and may be scarce). Fighter pilots and anti-aircraft gunners are traditionally more interested in learning how to use their weapons than aircraft recognition. If they survive they quickly learn better, for often enemy aircraft can look very much like your own. For example the North Vietnamese MiG-21 can look very much like the American F-4 Phantom. During the D-Day invasion the Allies painted broad black and white invasion stripes on all aircraft that would take part in the invasion. They knew that thousand of green troops would be on the ground, under fire and that many would not be able to tell a Spit from a Messerschmidt Bf-109. If it's not striped, shoot was the rule.
Second you establish clear Rules of Engagement about when weapons may or may not be used. Radio contact between differing units helps prevent friendly fire as one commander can tell another their location. Provided they've gotten it right, navigation errors are common among units in the field. Have you ever taken a wrong turn on a trip? Keeping on course is a lot harder when moving cross-country. Say you know you have some friendly troops around but you expect them to come from one direction. You spot infantrymen using cover moving from a different direction. Are they friend? Or foe? You try to call them on the radio but get no response? Are they enemy? Or has their radio broken? What are you going to do?
In combat Western armies like a bit of distance, preferring to use heavy firepower to destroy an enemy which cannot match their machines. Third World armies try to get as close as possible to their Western counterparts, to negate the westerner's big guns. If they're successful the Western commander may call fire in very close to front lines. Keep in mind that artillery battery supporting them is affected by rain, humidity, temperature, wind direction and the wear and tear on a gun that might be re-zeroed every few days. Shells fall short. Do you want to take that risk or do you wish to be overrun? Choose now while you still have the ability to choose.
Or you're a pilot of an F-16 Flying Falcon cruising over a battlefield at over 500 kph. You see flashes and smoke through the trees. You can hear the friendly commander on the ground and he sounds hard pressed. You glimpse what you think is an enemy APC moving down a mountain trail. Do you point your nose and shoot? Or do you go around for a second look knowing that APC might be about to penetrate your own lines? Or even worse, that they'll get a SAM ready to launch at your next pass? You have three tenths of a second to make up your mind.
Friendly Fire is of course a tragedy. The military is often reluctant to reveal friendly fire as a cause when their own men die from friendly guns. Partly it's out of embarrassment and partly because it somehow seems more honorable to fall to enemy guns. Family members take it better, as do the fallen soldiers' comrades. But friendly fire losses are not entirely avoidable during heavy combat operations. Events move too quickly and the stakes are too high for perfection. And so though armies will adopt careful rules of engagement and intensive training to try and minimize their losses. But they will never totally succeed in eliminating friendly fire.