In military terminology, friendly fire or fratricide is an unintentional attack by allied or neutral forces on friendly troops while attempting to attack enemy or hostile targets. Many NATO militaries refer to these incidents as blue on blue. Examples include misidentifying the target as hostile, cross-fire while engaging an enemy, and long-range ranging errors or inaccuracy. Accidental fire not intended to attack enemy or hostile targets, or deliberate firing on one's own troops for disciplinary reasons, is not called friendly fire, and neither is unintentional harm to civilian or neutral targets, which is sometimes referred to as collateral damage. Training accidents and bloodless incidents also do not qualify as friendly fire in terms of casualty reporting.
Use of the term friendly in a military context for allied personnel started during the First World War, often when shells fell short of the targeted enemy. The term friendly fire was originally adopted by the United States military; S.L.A. Marshall used the term in Men Against Fire in 1947. In classical forms of warfare where hand-to-hand combat dominated, death from a "friendly" was rare, but in modern warfare, deaths from friendly fire are more common.
Friendly fire is not to be confused with fragging, which is the uncondoned intentional (or attempted) killing of servicemen by fellow personnel serving on the same side.
Paul R. Syms argues that friendly fire is an ancient phenomenon. He notes recorded events in Ancient Greece and other early accounts of battles. He and other historians also note that weapons such as guns, artillery, and aircraft have dramatically increased friendly-fire casualties.
In the 20th and 21st centuries, friendly-fire casualties have become a significant percentage of combat injuries and fatalities. Jon Krakauer provides an overview of American casualties during and since the Second World War:
While acknowledging that the "statistical dimensions of the friendly fire problem have yet to be defined; reliable data are simply not available in most cases," The Oxford Companion to American Military History estimates that between 2 percent and 25 percent of the casualties in America's wars are attributable to friendly fire.
In the annals of warfare, deaths at the hand of the enemy are often valorized, while those at the hand of friendly forces may be cast in shame. Moreover, because public relations and morale are important, especially in modern warfare, the military may be inclined to under-report incidents of friendly fire, especially when in charge of both investigations and press releases:
If fratricide is an untoward but inevitable aspect of warfare, so, too, is the tendency by military commanders to sweep such tragedies under the rug. It's part of a larger pattern: the temptation among generals and politicians to control how the press portrays their military campaigns, which all too often leads them to misrepresent the truth in order to bolster public support for the war of the moment.
Although there may well be a longstanding history of such bias, Krakauer claims that "the scale and sophistication of these recent propaganda efforts, and the unabashedness of their executors" in Iraq and Afghanistan, is new.
Friendly fire can arise from the "fog of war" – the confusion and uncertainty inherent in warfare. Friendly fire that is a result of apparent recklessness or incompetence may be improperly lumped into this category. The concept of the fog of war has come under considerable criticism, as it can be used as an excuse for poor planning, weak or compromised intelligence, or incompetent command.
Errors of position occur when fire aimed at enemy forces may accidentally end up hitting one's own. Such incidents are exacerbated by close proximity of combatants and were relatively common during the First and Second World Wars, where troops fought in close combat and targeting was relatively inaccurate. As the accuracy of weapons has improved, this class of incident has become less common but still occurs.
Errors of identification happen when friendly troops are mistakenly attacked in the belief that they are the enemy. Highly mobile battles, and battles involving troops from many nations, are more likely to cause this kind of incident, as evidenced by incidents in the 1991 Persian Gulf War, or the shooting down of a British aircraft by a U.S. Patriot battery during the 2003 invasion of Iraq. In the Tarnak Farm incident in Afghanistan, four Canadian soldiers were killed and eight others injured when a U.S. Air National Guard major dropped a 500 lb (230 kg) bomb from his F-16 onto the Princess Patricia's Canadian Light Infantry regiment, which was conducting a night firing exercise near Kandahar. Another case of such an accident was the death of Pat Tillman in Afghanistan, although the exact circumstances of that incident are yet to be definitively determined.
During World War II, "invasion stripes" were painted on Allied aircraft to assist identification in preparation for the invasion of Normandy. Similar markings had been used when the Hawker Typhoon was first introduced into use, as it was otherwise very similar in profile to a German aircraft. Late in the war the "protection squadron" that covered the elite German jet fighter squadron as it landed or took off were brightly painted to distinguish them from raiding Allied fighters.
Errors of response inhibition have recently been proposed as another potential cause of some friendly-fire accidents. These types of errors are different from visual misidentification, and instead appear to be caused by a failure to inhibit a shooting response.
A number of situations can lead to or exacerbate the risk of friendly fire. Difficult terrain and visibility are major factors. Soldiers fighting on unfamiliar ground can become disoriented more easily than on familiar terrain. The direction from which enemy fire comes may not be easy to identify, and poor weather conditions and combat stress may add to the confusion, especially if fire is exchanged. Accurate navigation and fire discipline are vital. In high-risk situations, leaders need to ensure that units are properly informed of the location of friendly units and must issue clear, unambiguous orders, but they must also react correctly to responses from soldiers who are capable of using their own judgement. Miscommunication can be deadly. Radios, field telephones, and signalling systems can be used to address the problem, but when these systems are used to co-ordinate multiple forces such as ground troops and aircraft, their breakdown can dramatically increase the risk of friendly fire. When allied troops are operating, the situation is even more complex, especially with language barriers to overcome.
Some analyses dismiss the material impact of friendly fire, by concluding that friendly-fire casualties are usually too few to affect the outcome of a battle. The effects of friendly fire, however, are not just material. Troops expect to be targeted by the enemy, but being hit by their own forces has a huge negative effect on morale. Forces may doubt the competence of their command, and its prevalence makes commanders more cautious in the field.
Attempts to reduce this effect by military leaders involve identifying the causes of friendly fire and overcoming repetition of the incident through training, tactics and technology.
Most militaries use extensive training to ensure troop safety as part of normal coordination and planning, but soldiers are not always trained under possible friendly-fire situations to ensure they are aware of situations where the risk is high. Difficult terrain and bad weather cannot be controlled, but soldiers must be trained to operate effectively in these conditions, as well as being trained to fight at night. Such simulated training is now commonplace for soldiers worldwide. Avoiding friendly fire can be as straightforward as ensuring that fire discipline is instilled in troops, so that they fire, and cease firing, when they are told to. Firing ranges now also include "don't fire" targets.