History Main / FriendOrFoe

* In ''Recap/TintinTheRedSeaSharks'' Franchise/{{Tintin}} and his friends make an escape riding camels. Mull Pasha (Tintin's old foe Dr. Müller), head of Bab El-Ehr's forces, phones his air force commander to send a squadron of Mosquitos after them, adding "armoured cars are already on their way". Due to a misunderstanding, the Mosquitos fire on and destroy the armoured cars pursuing Tintin and co.!
* In ''ComicBook/TheAvengers'', after Hercules had been rendered comatose, Zeus brought the Avengers to Olympus and attacked them. A figure came to their aid, and Zeus fought him for some time, before he realized it was Hercules, risen from his sick bed to help his friends. Zeus is deeply grieved by his folly.
* The orkish view on friendly fire is seen in ''ComicBook/DeffSkwadron'', when the squad commander of deff skwadron chastises one of his gunners when he baulks at firing into a pitched dogfight where telling who is on which side is impossible. Essentially it boils down to "shoot at everything, and if you hit anything it must obviously belong to the enemy."
* In ''ComicBook/FuryMyWarGoneBy'', Nick Fury and his partner Heatherly is stuck on a French base in Vietnam, then called French Indochina. They come under heavy assault by the locals, and the battle gets close and messy. Eventually, the locals are driven back. After the battle, Heatherly says he's pretty sure he shot a friendly.
-->'''Nick Fury:''' I'm pretty sure I did too. Sometimes it just gets like that.
* When under the effects of the Trigger Scent, ComicBook/{{X 23}} enters a berserker state where she tears apart ''everything'' in her path, and when she's in her rage she blacks out entirely, and is completely unable to distinguish friends from foe. It's been exploited by villains on multiple occasions to force her to hurt people she cares about.

* In ''ComicBook/RobynHood'': I Love NY'' #3, Robyn and Agent Red are both sneaking into the same club. Not knowing who is coming, Red detonates a flashbang. Blinded and deafened, Robyn then attacks the person who threw the flashbang, not knowing it is Red.
* Played with in regards to ComicBook/TheIncredibleHulk as there are many instances where he's so enraged he's basically lashing out at whoever is in his vicinity, even if they were on somewhat genial terms before he started going nuts.
* Averted in ''ComicBook/BatmanYearOne'': when Branden's [=SWAT=] team are searching a ruined building for Batman, they prepare to fire through a suspiciously closed door. One of the officers gets on the radio and alerts the other officers that this is ''precuationary'' fire only.
* Discussed in the ''ComicBook/MarvelNOW'' launch of ''ComicBook/{{Thunderbolts}}''. When Agent Venom is recruited, he notices the other members are already in red and black and has the symbiote adjust, turning the white parts red. Deadpool calls him a suck-up, leading Venom to throttle him and tell him that using the same color lessens the chances of friendly fire.
* In ''ComicBook/JudgeDredd'', one of the tactics used by the Special Judicial Squad (the Judges' version of the Internal Affairs Bureau) is the "Random Physical Abuse Test", where a team of [=SJS=] Judges randomly abduct a Street Judge, drag them into a holding cell and torture them as an impromptu test of the Street Judge's ability to withstand interrogation. In issue #826, the problems with this test are highlit when the targeted Street Judge, having survived the events of Necropolis, presumes the attacking [=SJS=] Judges are assassins, grabs her gun, and shoots them dead on the spot. The plot of the issue revolves around the higher ups arguing about what's a suitable punishment for her, or even if she deserves a punishment.

* ''Film/ItTheTerrorFromBeyondSpace'' begins with Colonel Carruthers being rescued from Mars under suspicion of having murdered the rest of his crew. It's not helping his case that a skull was found with a bullethole in it, despite Carruthers saying they were killed by an alien monster. Carruthers admits that everyone was firing blindly when the monster first attacked them in a sandstorm, so he was presumably killed by a stray bullet, [[BetterToDieThanBeKilled which might well have been a mercy]].

* This sets up the plot of ''Film/{{Insomnia}}''. A detective hunting a murderer accidentally shoots his own partner and makes the mistake of covering it up. The murderer witnessed the incident and uses it to manipulate him to his own advantage.

** In in-game mechanics however, the trope is averted by the same vein as ''TabletopGame/{{Warhammer}}'', with no units being allowed to use ranged attacks upon units in engaged in a melee and risk hitting their allies. However, Blast weapons missing could potentially end up accidentally hitting allied units from scatter moving the targeting circle onto them.

* In the BackStory of ''Anime/MobileSuitGundam00'', Sumeragi and [[spoiler:Mannequin]] mistook each other's forces for the enemy and effectively obliterated their allies before realizing it. Both were deemed not at fault due to having been supplied with bad intelligence, but it still weighs heavily on both. Sumeragi's love interest died in that battle, too.
* In ''Anime/MobileSuitGundamWing'', the five Gundam pilots start out wary of each other and sometimes end up fighting among themselves after destroying their mutual enemy. None of them were told by their handlers that there would be others like them, so the HeelFaceTurn they all had concerning the objective of their mission prior to launch made them into each other's potential enemies, since they had no way of knowing whether the other Gundam pilots were still adhering to the original, rather genocidal mission plan. Unlike [[{{Fanon}} what the fandom would have you believe]], they don't come together as a five-man team until near the end of the series, but they do often work in pairs of varying combinations once the misunderstandings are cleared up.

* In the ''Anime/MobileSuitGundam'' sidestories known as [=MSV=], there is a Mobile Suit called the GM Camouf, which was a Zeon MS designed to look like a GM to fool the Federation. However, it proved to be a disaster when a group of Camoufs were destroyed by their own Musai transports!
** The modded "Zeta Zaku" by Iino in ''Anime/MobileSuitGundamZZ'' has a Zaku II's head in the place of the Zeta's (the Zeta's head was damaged and the Zaku was the only thing they had on hand for repairs). Comically, it's Judau who's confused and starts firing at it in his shock.

[[folder:Video Games]]
* This is particularly common in "real world" first-person shooters, particularly WWII shooters. Often, the only difference between the uniforms worn by the soldiers on your side and those worn by the soldiers on the enemy side are a slight difference in the shade of khaki. In sci-fi shooters, you at least have more flamboyant, easily distinguished uniforms, or the enemy will be outright alien and easy to spot simply by their profile.
** Happens so often in ''VideoGame/RedOrchestra'' to the point that there exists a specific apology message in chat.
* On the other hand, in a few shooters enemies can hurt each other with their attacks, the so-called [[http://www.giantbomb.com/monster-infighting/3015-2185/ monster infighting]] popularized by ''VideoGame/{{Doom}}''.
* Fortunately, many games give you the option of turning Friendly Fire off. Lag and collision detection glitches can also result in team kills while, say, firing on an enemy to assist with a kill if your teammate moves near your line of fire.
** Worse in ''Söldner'', where every player could customize his outfit and color, meaning only the teamnames above their heads showed who was on your team. Enter a bug where sometimes a teammate won't have this blue name displayed...
* ''VideoGame/AceCombat7SkiesUnknown'' has this as a running theme: who is friend and who is foe in a war where information is everything? For some specific examples:
** In Mission 9, the heroes are about to go home after a job well done when a flight of F/A-18s signaling as Osean planes arrives on the scene. Bandog tries to identify them only for the new arrivals to open fire on the 444th- [[spoiler: they're actually Erusean drones spoofing Osean [=IFF=] software in order to get in close to attack. Later, this same tactic is revealed to be how the Eruseans killed former President Harling and framed Trigger for it]].
** Near the beginning of the Third Act, the Erusean and Osean militaries attempt a decapitation strike by taking down the others' spy and communication sites. Problem is, the debris from the attack damage nearly every other satellite in orbit, essentially knocking out all advanced communications on Strangereal in general and Usea in particular. The communication breakdown sees Erusea descent into a civil war as Radicals, Conservatives, and anti-Erusean militias rise up and start shooting everything that moves, and a fair number of Osean forces also turn on one another due to the confusion. In these missions, the player has to manually identify friendly and hostile units via brief missle lock, long enough for [[MissionControl AWACS]] to properly code them.
* ''VideoGame/CallOfDuty'' has this problem as well -- it's surprisingly easy to get the game to not display a teammate's name over his head even as you're staring right at him, though thankfully there's normally no friendly fire. Then you enter Hardcore mode, where friendly fire is enabled, the name-tags are disabled, there's no radar to show teammates' locations unless a UAV or spy plane is in the air, and health is reduced to the point that a single bullet with pretty much anything is an instant kill. Getting kicked from the server for too much accidental teamkilling is not at all uncommon.
** Regarding ''Call of Duty'', the single player campaigns have some of the same problems; the names of allied [=NPC=]s are often not displayed if you're not aiming at them or at a distance. The games try to acknowledge the inherent risk by allowing the player to accidentally/[[VideoGameCrueltyPotential deliberately]] wing plot-relevant allies (who will often give a word of warning) or kill the occasional RedShirt, but this isn't always consistent; add in some ArtificialStupidity, and you'll probably have a few unnecessary game overs on your hands.
** Done twice during the mission "Second Sun" in ''VideoGame/CallOfDutyModernWarfare2'', where [[spoiler:the effects of a nuclear missile going off over Washington, D.C.]] have caused a blackout and rendered all forms of communication beyond verbal a no-go. The first person the player's squad meets afterwards turns out to be a runner who simply forgot the [[TrustPassword Rangers' countersign]], who rallies the squad to head for the White House. Afterwards is a very intense scene when a lightning strike reveals a group of soldiers crossing the street some thirty meters in front of the squad. They don't immediately reply to the countersign by Sergeant Foley, and suddenly guns are firing everywhere as it turns out they're Russian soldiers.
* ''VideoGame/ASPAirStrikePatrol'' {{Deconstruct|edTrope}}s the "shoot anything that moves" aspect of {{Shoot Em Up}}s this way. Coalition forces and civilians are present throughout the game, and some missions will require you to make precise strikes on enemy forces in urban areas. Hitting friendlies or civilians ''will'' make international news, and damage public opinion of the Coalition. Do it enough, and anti-war protests will happen. Ultimately you'll earn yourself a NonstandardGameOver as the Coalition is forced to pull out.
* In ''VideoGame/{{Fallout 1}}'', you had to take a separate perk to have the computer mark your friends in green. Without it, you had to remember (or, in some cases, guess) who was on your side. Or you could just "check". If the game tells you "Ian", "Tycho", "Katja" or "Dogmeat", chances are good that they are friendly.
** In ''VideoGame/FalloutNewVegas'', while wearing [[DressingAsTheEnemy Faction Armor]], opposing factions will be hostile to you, regardless of your reputation with them.
* The main reason to play as an Engineer in ''VideoGame/MassEffect1'' or ''VideoGame/MassEffect2'' is to scramble enemy robots' IFF targeting and make them go on a berserk rampage through their own side.
** This is also how Samara greets Shepard for their first meeting in ''Mass Effect 2''.
* In ''VideoGame/{{Fable}}'', firing on a neutral character causes them to decide that the player is trying to kill them, and they promptly attack.
** ''Fable'' has a ''huge'' problem with this. Trying to win any large-scale battle with non-scripted allies is virtually impossible because they end up flashing red any time the player hits them- even if it's in such a way that neither the player nor the ally has any way of knowing where the shot came from!
* ''Franchise/TheElderScrolls'':
** Throughout the series, allies and escorts with ranged attacks or spells have no compunction against using them, even if you are current between them and their target. This gets even worse if they have large AreaOfEffect spells...
** This is one of the contributing factors to ''[[VideoGame/TheElderScrollsIIIMorrowind Morrowind]]''[='s=] notorious {{Escort Mission}}s. The SuicidalOverconfidence of your escortees mixed with their ArtificialStupidity leads to them [[LeeroyJenkins running off to attack every enemy in sight]]. If the enemy doesn't outright kill them, a stray blow from you likely will. If they survive it, there is a good chance they will then turn on you for attacking them. Either way, mission failed.
** ''[[VideoGame/TheElderScrollsIVOblivion Oblivion]]'' attempts several methods to downplay this trope. For one, those you are escorting are typically tagged as "essential", meaning they can't be killed, only knocked out. Additionally, the AI is a lot more understanding with accidental hits (with {{N|onPlayerCharacter}}PCs just admonishing you for being sloppy, unless you hit them quite a few times in a row). Finally, ''Oblivion'' includes a method for yielding to [=NPCs=] you've accidentally made hostile.
* The original ''VideoGame/{{Diablo}}'' game had friendly fire enabled.
* It's quite difficult to avoid hitting fellow survivors in ''VideoGame/Left4Dead'' (well, [[TheComputerIsACheatingBastard except for the AI]], which is good for you because otherwise they would be '''really''' bad at not downing you). There's even an achievement, "Safety First", for getting through a campaign without any friendly fire incidents. As of May 2017, [[http://www.steampowered.com/status/l4d/ only 4% of the players]] have acquired it.
* In ''VideoGame/WingCommanderPrivateer'', it's trivially easy to fall afoul of this with the starting radar, which doesn't give target types any color coding; the militia forces fly the same ships (with different color schemes that are hard to notice until you're right next to them) as the [[SpacePirates pirates]] and [[SpaceAmish Retros]], further compounding the problem. More advanced radar models color-code contacts, making it much easier to determine who is or isn't a legitimate target.
** In the main games, for the most part your opponents will be flying ships entirely different from your own side's, so it's easier to tell who's who. This doesn't, however, help too much if your [[ArtificialStupidity wingman]] flies right into the path of the torpedo you just launched, resulting in an insta-kill of said idiot and everyone else declaring you a traitor, in all but the very first game (where there's no penalty for killing your wingman).
*** On a related note: during a mission briefing in the original game, one wingman "Maniac" is so much trouble that the player is given permission to shoot him if he gives you too much hassle. There is also a Friend or Foe missile used throughout the series that locks onto targets if it doesn't broadcast the right friendly comm code, however the comm system can get damaged in fights.
* Taken to an extreme in ''VideoGame/TeamFortress2''. While it is very easy to see who is friend or foe due to the brightly colored team uniforms, the Spy class has the ability to disguise as any other class and in the process take on the name of another player. As the Spy also has an instantly lethal back-stab attack and it's not always too easy to notice the spies on behavior alone, it has become common to "spy-check". That is, shoot at your own team, preferably at close range. Anyone who dies or starts running, [[MemeticMutation IS A SPAH!]]. This is because [[FriendlyFireproof you can not hurt your own team]]. The best class for spy-checking is the Pyro, as a quick puff of flame will render both the Spy's disguise and his [[InvisibilityCloak invisibility watch]] useless. Pyros are in fact expected to [[KillItWithFire set fire to anyone and anything]] in order to find spies, and a Pyro who does not do this will most likely be subject to a spy-check himself.
** Averted in the Spy's own "Meet the Spy" video. The Soldier's point-blank shotgun blast would have been a perfectly valid tactic in game, resulting only in a BLU spy annoyed at being interrupted mid-monologue. Instead, the Spy's head explodes in a shower of LudicrousGibs.
* Averted in ''VideoGame/CommandAndConquer: Red Alert 2'' and ''Red Alert 3'', Allied Spies and/or Imperial Sudden Transports can disguise themselves as enemy units, but will [[FriendlyFireproof never be mistakenly fired on by their own side]]. The only way for an enemy to attack them without using scouts to break their disguise is to force-attack (explicitly give orders to attack, as units without orders will not engage them). Yuri's mind control towers, however, immediately FaceHeelTurn spies as soon as they hit their effective range.
* Some stages in the ''VideoGame/{{Gauntlet}}'' series of games had this, where your shots could either stun or even harm other players.
* Side-scrolling beat-em-ups, such as ''VideoGame/FinalFight'', also have this. Even ones that did not (such as the Franchise/TeenageMutantNinjaTurtles or Franchise/XMen games) would have certain special wild attacks (respectively, environmental attacks and hurled enemies) that could harm other players.
* ''VideoGame/{{Doom}}'' had friendly fire in co-op mode. Much more famously, any monster with a projectile could incite a riot by accidentally hitting its allies, which would cause them to forget all about the player and kill each other. They don't really notice if one of their buddies wanders into the line of fire. Quite a bit of Doom strategy is based around tricking enemies into hitting each other.
* ''VideoGame/GwentTheWitcherCardGame'': Many card effects indiscriminately hit either side of the board. It's a common rite of passage in the game for ignorant newbies to accidentally obliterate their own units.
** Scorch, which destroys the highest unit(s) on the playing field is the prime offender of this. It's gotten to the point that there are message boards dedicated to explaining that if the highest unit is on your side it will be destroyed. To a lesser extent this applies to epidemic which targets all of the lowest unit(s).
* ''VideoGame/StarFox64'' had a mission on Katina that, in addition to being a ShoutOut to ''Film/IndependenceDay'', involved assisting a Cornerian Defense Force base's fighter compliment in fending off Andross' forces. The problem -- Andross' fighters are designed nearly identically to the CDF "greenies", and they are both easy to destroy with the Arwing's lasers. Fox's CDF friend Bill will not hesitate to [[WhatTheHellHero call Fox out]] if he shoots down a CDF fighter.[[note]]One way to tell them apart is to try locking onto them: only enemy fighters register as valid targets.[[/note]] \\
\\
Though rare, it's possible for the ''rest'' of the Star Fox team to shoot down the CDF fighters as well.
-->'''Peppy:''' Enemy down ... Wait! ''That was one of ours!''
* This is a major danger in the ''VideoGame/TotalWar'' series, particularly with siege units.
* Set ''VideoGame/DragonAgeII'' to [[HarderThanHard Nightmare]] difficulty level. Put a two-handed warrior with a BFS and a blaster mage with area-effect spells in your party. Let the AI control them while you muddle around as some other character. Watch the TotalPartyKill ensue.
* ''VideoGame/ChivalryMedievalWarfare'' has serious problems with this, mostly because all battles eventually turn into multi-man melees with archers firing into the fray. And when you swing any sort of weapon into a fray that size, you're eventually going to chop your ally's head off by accident. Archers don't have it any better, and unless you're really good a sizeable portion of your arrows will end up adorning your pals. Even with proper caution taken it's very, very hard to avoid decking someone on your side during any battle bigger than a three-on-two.
* As per the ''Chivalry'' example above, it's also possible to accidentally hit allies with projectile weapons in ''VideoGame/MountAndBlade''. Don't fire/throw into melee, it's just not going to end well. Fortunately, melee attacks can't harm your allies, though weapon swings will probably bounce off them (similar to swinging at a wall, for instance).
* ''VideoGame/{{MORDHAU}}'', being a spiritual successor to ''Chivalry'', would naturally have its share.
** In big frays, hitting your teammate because you were swinging a big-ass maul around is basically inevitable if it gets beyond 3 against 1. Stabbing has less possibilities, but not every weapon is good at that, and even ''then'' it's perfectly possible for one of your side to get in the way and get shanked to death. And the less said about firing into a massive fray, the better. There's even a perk to reduce friendly fire damage by 50%, which is almost a ''must'' for certain builds. And since it also dampens friendly fire that ''you'' take, it's still recommended for when you just can't trust your teammates to aim their [[{{BFS}} giant sod-off zweihander]] anywhere that isn't your back. And there's even voicelines for both callign out a teammate for hitting you and apologizing after hitting a teammate, though not all of the latter are friendly...
-->'''Raider voiceset:''' Have you seen [[{{BFS}} the size of this fucking sword]]!? Of course yer gonna get clobbered if ya stand next to me ya ''tit''!
** And then there's siege weapons. Ballistae are bad enough, what with how they just keep going until they hit a wall; shooting them into a melee is one way to get a multicolored shishkebab. And catapults and mortars... it's pretty much impossible to ''not'' kill one of your guys with a shot unless you're very good or very lucky. Prepare to be literally kicked off the siege engine in question if you do it too much, especially if you wipe out half your team in one EpicFail of a shot.
* One of the more embarrassing things to happen to players using howitzers in ''VideoGame/WorldOfTanks'' is this--because howitzers (including artillery guns) are both hideously inaccurate ''and'' devastatingly powerful, there's very few arty players who haven't accidentally teamkilled an ally thanks to the terrible accuracy on their gun.
** Alternatively, you could have your sights on an enemy that was "tracked"[[labelnote:Definition]]Short for "de-tracking", or rendering a vehicle immobile by way of destroying its tracks.[[/labelnote]] long enough for your crosshair to lock in a guaranteed direct hit, only for them to fix it and run off ''after'' you've fired, at which point an ally just so happens to stop right in the middle of your aim. Direct hit, ally goes kaboom, see you back at the garage.
** Light tanks tend to be the biggest receivers of this trope. Not just because of artillery, but because they can be so busy running circles around Tank Destroyers or Heavies, that they aren't paying attention to the guns of their own team-mates. This can result in many cases of Friendly Fire while team mates fire on enemy tanks while unaware that an allied Light Tank is about to come screaming around like a jackrabbit on crack.
** In ''VideoGame/WorldOfWarships'', Torpedoes are basically addressed "To whom it may concern" as missed torps that haven't sputtered out or hit their intended mark can be just as lethal to an ally, as they can to an enemy. There's even been cases of particularly careless carriers with torpedo bombers sinking ''themselves'' with their own torpedoes.
* This can be a bit of a problem in some flight simulators, especially those taking place in the UsefulNotes/ColdWar Middle East. For instance, in ''F-15 Strike Eagle'' it is possible to play missions against Iran, who can and will field the American-built F-4 Phantom and F-14 Tomcat. The problem is that, since you play an American strike fighter, your allies are ''also'' in Phantoms and Tomcats. Any pilot with a too-itchy trigger finger who doesn't obey the rules of engagement (identify, then engage) will come home to find a nice neat court-martial summons waiting for them.
* This can happen in ''VideoGame/{{XCOM2}}'' during Retaliation missions. The VichyEarth would not hesitate to shoot at civilians for the simple crime of not living under their rule. And they send some {{Shapeshifter}} infiltrators to make rescuing them harder for LaResistance. But sometimes, civilians run away from enemies, and sometimes, they trigger reaction fire from enemies who used the overwatch order (an order that makes them shoot at the first enemy that moves). Faceless act exactly as civilians until your soldiers get near them, or all the other Vichy Earth troops are killed. And sometimes, they get shot by their own allies while running away.
* In ''VideoGame/HalfLifeAlyx'', [[MissionControl Russell]] pilots a hacked Combine Scanner to help guide Alyx to his hideout early on. It gets destroyed, but he manages to repair it midway through the game. Except he doesn't tell Alyx he's done this, and as the drone [[JumpScare pops in very suddenly]] and can potentially be mistaken for a Manhack it's possible for a particularly TriggerHappy player to put several rounds into it before they realize it's friendly. Fortunately, it's FriendlyFireProof, so no harm done, but still.
* ''VideoGame/DeepRockGalactic:'' While it's easy enough to tell the dwarves apart from any enemies, when fighting against absurdly huge hordes of bugs in tight quarters does inevitably lead to some friendly fire incidents. Some weapons, like the Engineer's Grenade Launcher and ''especially'' the Driller's Satchel Charge naturally have more problems, due to explosion radius and the usual panic in which they're tossed out. At least there's perks to mitigate friendly fire damage, though the dwarves themselves will still get pissed.
-->''"'''TRIGGER DISCIPLINE''', ya whale piper!"''
[[/folder]]

[[folder:Literature]]
* ''Artificial Condition''. Twice when [[Literature/TheMurderbotDiaries Murderbot]] goes into action one of the men it is fighting accidentally kills another in the confusion. Then for a RuleOfThrees Murderbot uses their boss as a BulletproofHumanShield against gunfire from her own bodyguard.
* In ''Literature/ABrothersPrice'', Jerin threatens to shoot Cira while he's escaping. She barely manages to get past the gun; then she [[TheMole helps]].
* Discussed in ''Literature/ArkRoyal'', where the titular old-fashioned [[TheBattlestar armored carrier]]'s sensors are so bad that the automated [[PointDefenseless point-defense]] guns have a good chance of mistaking one of the carrier's own fighters for an enemy and shooting it down. Unfortunately, since the aliens' stealth systems are so good they can easily bypass a fighter screen to strike at the ship herself, the ship's CAG orders that at least one wing must always remain close to the carrier to protect it, despite the risk from the point-defense guns.
* In Creator/LoisMcMasterBujold's ''Literature/CaptainVorpatrilsAlliance'', Ivan explains they still use dog tags to identify soldiers because implants might betray them to their enemies.
* In Creator/CSLewis's ''Literature/TheSilverChair'', having killed [[spoiler:the Lady of the Green Kirtle]], they set out warily into her underground kingdom -- her subjects are setting off firecrackers, and they fear signals -- but once they capture one to question, [[spoiler:Rilian reveals that he killed "Her Ladyship", the subjects reveal they were under MindControl]], and matters are settled all around.
* In Creator/RobertEHoward's "Literature/BeyondTheBlackRiver" Franchise/ConanTheBarbarian talks to a Pict in his own language to trick him ashore so he can kill him and steal his boat -- to BringNewsBack of the Pictish attack.
* In ''Franchise/TheDarkTower'' series, Roland mentions that he and his best friend Cuthbert killed their friend Alain after mistaking him for an enemy scout.
* In one battle in ''Literature/TheDiamondThrone'', a force masquerading as Pandion Knights is attacked by a force of legitimate Pandions. As both sides would be in the same armor design, the legitimate Pandions wear colored armbands to identify friend from foe.
* Creator/TerryPratchett's ''Literature/{{Discworld}}'':
** Asked by a [[TheGuardsMustBeCrazy palace guard]] when Mort, channeling [[TheGrimReaper Death himself]], tries to enter.
--->'''Guard:''' Friend or foe?\\
'''Mort:''' Which would you prefer?\\
'''Guard:''' ...Pass, friend.
** In ''Literature/InterestingTimes'', the {{Magitek}} terracotta warriors springing up beneath [[BigBad Lord Hong's]] army causes the soldiers to flee... towards the armies of his rival Lords who only joined forces because 7 barbarians had taken over TheEmpire. The soldiers assume that they're being attacked by Lord Hong and start fighting. It's noted later that these fights actually killed more of the soldiers than the terracotta warriors.
** In ''Literature/{{Jingo}}'', while Vimes is having a talk with 71-hour Ahmed in Klatch, they are attacked by a random Ankh-Morpork patrol looking for Klatchians to fight.
** ''Literature/{{Night Watch|Discworld}}'' has a group of the old City Watch defending Sam Vimes, while another group of Watchmen (led by an escaped criminal) are trying to kill him. The friendlies happen to be passing a lilac bush, so they each break off a blossom and stick it on their helmets. This becomes [[UsefulNotes/ThePoppy a tradition in later years]], with the survivors of the battle [[DueToTheDead wearing the lilac]] every 25th of May.
* ''{{Literature/Doom}}'' begins in Afghanistan where Fox company is lost in a mist. The company sees shadowy figures moving around and Lt. Weems panics and orders the Marines to attack. Arlene, the company scout, has gotten in close and confirmed that the men are unarmed monks. Weems refuses to listen, Fly tries to punch him out but fails, and Fox guns down civilians in a fog.
* In Creator/JimButcher's Literature/TheDresdenFiles novel ''Literature/DeadBeat'', [[spoiler:GrandTheftMe]] makes this very difficult to figure out.
* In Creator/WenSpencer's ''Endless Blue'', Mikhail immediately deploys Reds to guard on the crash; when he is asked what if someone approaching was friendly, he says they will learn that they are ''not''. He tones down the orders shortly. An officer complains that they can not use IFF -- Identification Friend or Foe -- to recognize anyone, and Mikhail orders maintaining radio silence, which will keep anyone from finding them.
* Happens in accordance with [[TruthInTelevision historical incidents]] of friendly fire in Jeff Shaara's [[UsefulNotes/AmericanCivilWar Civil War]] novels, ''Literature/GodsAndGenerals'' and ''Literature/TheLastFullMeasure''. General "Stonewall" Jackson is shot in ''Gods'' by fidgety sentries and dies of complications. General Longstreet is shot in ''Measure'' right after worrying that one rebel unit's black uniforms make them look like Yankees, but he eventually recovers.
* At the end of ''A Good Clean Fight'' by Creator/DerekRobinson, a (British) SAS patrol is ordered to intercept the survivors of a German bomber that landed out in the desert. They do, and capture the crew. A (also British) fighter squadron has received the same orders, but when they reach the bomber they see that someone's been there before them. They follow the tire tracks -- and thoroughly strafe the SAS patrol and kill everyone they see. [[TruthInTelevision It happened]].
* Part of the formula of ''Literature/TheHardyBoys'' series has the heroes, at the climax, briefly mistaking TheCavalry for enemy reinforcements.
* In Creator/EdgarRiceBurroughs's ''[[Literature/JohnCarterOfMars The Gods of Mars]]'', John Carter, trying to escape, attacks the approaching jailor -- only to realize that it wasn't the jailor, it was his own son. Briefly, he even thought he had killed him.
* In Creator/EEDocSmith's ''[[Literature/{{Lensman}} Triplanetary]]'', in the Atlantis section, Phryges is held at gun-point by a woman while he is undercover -- and he realizes it's his childhood friend Kinnexa. She insists on his turning around so she can check for a scar to be sure it's him.
* In Creator/HBeamPiper's ''Lord Kalvan of Otherwhen'', Kalvan discusses {{battle cr|y}}ies to keep their forces from attacking each other. At the battle itself, some of their foes attack others on their side; after it, Kalvan talks with one prisoner, who indignantly declares that he had been shouting his battle cry at the top of his lungs.
* In Creator/PatriciaCWrede's ''Literature/MairelonTheMagician'', Kim is accosted as she comes out of the pub, and blacks his eye before she realizes it's Mairelon.
* In Creator/PoulAnderson's ''Literature/AMidsummerTempest'', trying to reach the royalist forces brings up great fears of this being a problem; Rupert thinks he should not try to cut his hair so he can prove who he is, quickly.
* In Creator/EdgarRiceBurroughs's ''Literature/TheMonsterMen'', Sing shoots at ships he takes for pirates, though he knows they might not be, because being taken by pirates is too horrible to risk.
* In L. Jagi Lamplighter's ''Literature/ProsperosDaughter'' trilogy, at one point, someone pursuing Miranda by boat suffers a fatal accident on rocks. Only later does she learn he was one of her brother's men, trying to warn her of something.
* ''A Sailor of Austria'' by John Biggins.
** Lt. Otto Prohaska receives orders to shell enemy forces in a small harbour that isn't even on his maps. He turns up at where he thinks is the enemy area and starts shelling it with the deck gun, doing only minor damage, when the lookout suddenly realises they're shelling their own troops, so they quickly submerge and get the hell out of there. Later Prohaska reads in a newspaper about how his submarine bravely attacked an enemy harbour, causing such massive damage that the cowardly enemy fled in terror. ''In the same paper'' is an article about the brave Austrian soldiers who sank an enemy submarine who opened fire on them while [[DressingAsTheEnemy treacherously flying the Austrian flag]].
** Later the German navy accuse him of torpedoing one of their mine-laying submarines that had gone missing, one that had his future brother-in-law serving on it as well. His fiancee doesn't hold it against him as accidents happen in war, and Otto is eventually cleared of the accusation, but he lives with this doubt for years until he finally comes across proof that the submarine blew itself up with a malfunctioning mine.
* In Creator/MichaelFlynn's ''[[Literature/SpiralArm In The Lion's Mouth]]'', a secret espionage war has friendly fire accidents: one man is killed by another on his side, because of his cover. Later, Dominic Tight is targetted [[spoiler:in an actual fight, where his invisibility cloak hides his identity.]]
* This happens in ''Franchise/StarWarsLegends'' novels as the Galactic Civil War progresses, particularly in works like the ''Literature/XWingSeries''. Due to VehicularTurnabout, the Rebels/New Republic end up using an increasing amount of Imperial military hardware, from captured Star Destroyers to [[MookMobile TIE Fighters]] (though in the latter case the Rebels try to put as many DeflectorShields on the starfighters as possible, along with painting large, bright red Rebel starbird emblems on the solar panels). So veteran pilots get to deal with lingering nervousness as they approach a friendly Star Destroyer, and in some battles squadron leaders have to tell their pilots not to take a snap-shot at any TIE until their targeting computer confirms it's an enemy. Wraith Squadron in particular, due to their success with TheInfiltration of enemy forces, has a few close calls when an X-Wing pilot sees the TIE in their crosshairs flip from a red to blue target.
* Franchise/TolkiensLegendarium:
** In ''Literature/TheChildrenOfHurin'', Túrin, having been captured by Orcs [[spoiler: mistakes his best friend Beleg, who has come to rescue him, for one of his captors and kills him]]. This triggers a major HeroicBSOD.
** In ''Literature/TheReturnOfTheKing'', the sight of the fleet causes panic in Gondor until its flag becomes clear.
* ''TabletopGame/Warhammer40000'' books:
** In Creator/JamesSwallow's Literature/BloodAngels novel ''Deus Encarmine'', many Blood Angels, driven into the Black Rage, fall blindly on each other -- an effect that the survivors [[HeroicBSOD actually admit]] [[LosingTheTeamSpirit frightened them]]. When they counter-attack and take down the enemy ship, the Word-Bearers' helots are driven mad by the psykers' deaths and fall on each other -- blocking the Word-Bearers' way, so they slaughter them, too.
** In Creator/SandyMitchell's Literature/CiaphasCain novel ''Death or Glory'', when he made vox contact with Sergeant Tayber, Tayber refused to give him his position because he didn't know he was really a commissar, and went to meet him instead; this gives Cain hope that he has hit on a competent officer. Later, Lieutenant Piers is about to open fire on their [[DressingAsTheEnemy orkish vehicles]], and when Cain hails them, still demands that he prove it.
** In Creator/DanAbnett's Literature/GauntsGhosts novel ''Only In Death'', in an apparently haunted stronghold, the Ghosts repeatedly bring up guns only to discover they were about to shoot their own men. No friendly fire occurs, although sometimes because another soldier stops it.
*** In ''Blood Pact'', Criid attacks a figure in the streets; he wrestles with her until he can point out that he's Gaunt.
** In Creator/GrahamMcNeill's Literature/HorusHeresy novel ''False Gods'', Davin's moon is so mist-bound that Loken is always bringing up his gun to shoot before he recognized an ally. More seriously, remembrancer Petronella Vivar takes it upon herself to go to the battlefield, and her shuttle goes unrecognized and is fired upon.
*** In Creator/JamesSwallow's ''The Flight of the Eisenstein'', Garro refuses to shoot on a Thunderbird without hailing it to find out why.
*** In Creator/GrahamMcNeill's ''Fulgrim'', Lucius [[spoiler:[[TurnCoat having betrayed them to Horus]], tricks Captain Demeter into helping him kill the loyalist Space Marines with him.]]
** In William King's ''Literature/SpaceWolf'', when Ragnar escapes the [[{{Mordor}} caves]], he faces a lot of guns in the hands of Space Marines. Although he thinks they recognize him, he is very, very, very careful, because it would be irony indeed to escape the Chaos Space Marines to die at the hands of friends.
*** In ''Grey Hunters'', they find soldiers, and Ragnar spies on them to discover that they are loyalist. He is very careful about contacting them, in order to avoid provoking a fight.
*** In Lee Lightner's ''Sons of Fenris'', when Ragnar is leading Space Wolves in the jungle, they reach the city, and find that the comms don't work, and they are taken for enemy. Ragnar has to charge through the attack to make contact. Later, when Ragnar [[TheNoseKnows smells]] that there are other Space Marines in the city, he and the rest of the Wolfblade ready for combat, just in case.
** In Creator/GrahamMcNeill's ''Storm of Iron'', the Chaos forces herd prisoners toward the Imperial outpost. They are slaughtered, and the forces learn the positions of the Imperial guns.
** In Creator/DanAbnett's ''Literature/{{Titanicus}}'', Cally Samstag had the troopers [[YouAreInCommandNow flee after one of them sent a message]]. They are still tracked down by skitarii. When they ask for them to GetItOverWith, the skitarii say they have sent for a rescue and then realizes that they thought it was an enemy.
** In Creator/GrahamMcNeill's Literature/{{Ultramarines}} novel ''Dead Sky, Black Sun'', after a fight, [[spoiler:the Unfleshed]] take Uriel and his companions prisoner because they might be friendly -- though they think probably not.
*** In ''The Killing Ground'', when the Space Marines make contact with Imperial forces, they first scout them carefully; Pasanius assures Uriel that their machinery is well-maintained, which points toward Imperial forces, but they still meet them with some trepidation, as there is no way to be sure. Later when the Grey Knights arrive, they take Uriel and Pasanius prisoner -- none too gently -- because they might be tainted and so enemies.
** In Andy Hoare's Literature/WhiteScars novel ''Hunt for Voldorius'', the Raven Guard, seeing someone arrive, discuss the possibilities -- not allies of the Chaos forces, since they arrived secretly, but they could be Chaos forces that are rivals, and they don't see any way they could be Imperial. It is fortunate that one White Scar scout made out some of the Raven Guard and voxed an abort to the Thunderbirds, and the Raven Guard intercepted it; there was nearly a fratricidal bloodbath.
* In Creator/LloydAlexander's ''[[Literature/{{Westmark}} The Kestrel]]'', a battle-mad Theo shoots a Regian soldier before he realizes it's actually his queen (and, to make it worse, his betrothed) DressingAsTheEnemy.
* At one point in ''Literature/TheWheelOfTime'' series, Rand's attempt to secure the allegiance of the [[ProudWarriorRace Aiel clans]] has caused a civil war among that race, and he has to put down the rebellious faction before they can lay waste to civilization. The Aiel on his side are convinced to wear armbands so that the non-Aiel forces know not to attack them; they take this as a great insult, as they can tell one clan from another at a glance from the cut of their clothing.
* In ''Literature/TheWinterWar'' by Antti Tuuri, many cases of confusion occur.
** A group of Russians walk right through the Finnish lines in the dark, thought to be tired and grumpy Finnish combat engineers when they don't answer the password challenge. The narrator thinks the Russians themselves were unaware of what happened and believed the Finns had already withdrawn further.
** A story is heard about a Finnish pilot who makes a forced landing between the lines and is fired at from both directions, and being wounded and confused, he himself can't tell where the friends are since there's a Swedish-speaking unit on the Finnish side.
* ''Harry's Game'' by Gerald Seymour involves an undercover agent being sent to infiltrate Belfast to catch an IRA gunman. He eventually catches his quarry and shoots him, only to be shot himself by a British army sniper (who from his point-of-view saw one civilian shoot another). The authorities issue a deliberately vague statement to make the press think it was a MutualKill instead.
* ''KG 200'' by J.D. Gilman and John Clive is about a Luftwaffe unit that specializes in flying captured Allied aircraft. It opens with an American bomber that's been fatally damaged by German flak, and it's only gradually revealed that the crew is German also and they were meant to be dropping spies over England. Later as word of the fake Allied planes gets out, the gunner on an Allied bomber shoots down another bomber that's behaving suspiciously. Turns out it really was a friendly, but their commanding officer pretends they made the right decision to preserve morale.

[[/folder]]

[[folder:Real Life]]
[[/folder]]

* The rules of heraldry exist to avert this trope.
* It has been estimated that during any particular war since the dawn of the gunpowder era, as much as ten percent of the casualties were the result of this trope.
* "At least" would be appropriate. People playing "scenario" paintball (in the woods with ambushes and camo, as opposed to open field with team-colored shirts and short-range engagements) and airsoft realize very fast how ''the only thing more accurate than incoming enemy fire is incoming friendly fire'' indeed.
* During the Battle of Chalons in 451 AD, after the Visigothic King Theodoric had died, the Visigoths and Romans had managed to fight Attila the Hun to a standstill into the night. In the darkness, Thorismund, the new Visigothic king, was nearly killed when he rode toward Hunnic lines thinking they were his own soldiers. Luckily for him, he realized the truth in time and booked it. This was mere hours after his father died. The Visigoths almost lost two kings in a single battle.
* OlderThanSteam: During [[https://en.wikipedia.org/wiki/Battle_of_Barnet the Battle of Barnet]] in 1471, a Lancastrian force under the Earl of Oxford was fired on by the Lancastrian centre while returning from a pursuit; their banner, Oxford's “star with rays” had been mistaken for the Yorkist “sun in splendour”. This gave rise to cries of treachery (always a possibility in that chaotic period), Lancastrian morale collapsed, and the battle was lost.
* One [[http://en.wikipedia.org/wiki/Battle_of_Kar%C3%A1nsebes urban legend]] concerning an event in the Hapsburg-Ottoman wars of 1787-91 ramps this up to EpicFail levels. Between drunkeness, [[PoorCommunicationKills lack of communication]], and darkness two Austrian forces both end up thinking they are under Turkish attack; when the Turkish army showed up a couple of days later they find 10,000 casualties and the rest long gone so they take the nearby town with hardly a shot.
* Confederate general Stonewall Jackson was shot by some of his own men and mortally wounded when they mistook him for a Yankee in the dusk when he returned from a reconnaissance ride late during the battle of Chancellorsville (1863).
** This was a real problem for much of UsefulNotes/TheAmericanCivilWar. Confederate soldiers in particular tended to wear non-standard uniforms, due to their government generally being less organized and specifically having serious problems supplying the troops. If you didn't have an overcoat you might take one off a dead or captured Yankee. Combine that with poor communications in a pre-radio era and the huge amounts of smoke produced in combat, and the general confusion caused by combat, and Friend Or Foe happened many times.
** Further problems were caused by the original flag of the Confederates still bieng a variation of the Stars and Stripes, which lead to the many redesigns that finally settled on one based on the battle flag of a Tennessee regiment.
* During UsefulNotes/WorldWarI, being shelled by your own side's artillery was such a big and common hazard, that in the German army there was a much-used saying: "Der schlimmste Feind der Infanterie/Das ist die eigene Artillerie" (The worst enemy of the infantry is the own artillery). The fact the general method for attacking enemy positions during the war was closely behind artillery shelling them certainly did not help.
** A deliberate version happened on the last day of the war, when one artillery battery kept firing on the Germans despite having been told the armistice had been signed. It took the threat of being fired on by allied artillery to get them to stop shooting.
* UsefulNotes/WorldWarII also had its share of incidents:
** The United States did field tests of the practicality of camouflage uniforms. They took a handful of infantry, fitted them with uniforms, put them on the front and see how things turned out. Well, the Germans were the only ones in the theater that had their infantry use camouflage uniforms in appreciable numbers. With that knowledge and the fact that it's on this page, it shouldn't be surprising that most the infantry involved in the test decided to trade in their experimental uniform for the standard issue.
** The American Navajo Code Talkers' bodyguards were not, as legend had it, to kill them in case of capture. The bodyguards were to protect the Code Talkers from other American soldiers. In the Pacific, a not-obviously-white man talking a strange language was automatically assumed to be Japanese, and many Code Talkers were shot at or arrested as spies. Assigning white soldiers aware of the otherwise-secret Cold Talkers to the Navajo solved this issue.
** In Antony Beevor's book ''D-Day: The Battle for Normandy'' he retells a German joke (from the fighting on the Italian peninsula) made at the expense of the RAF, Luftwaffe, and USAAF -->"If British planes appear, we take cover. If the Luftwaffe appears, nobody takes cover. And if the Americans show up, ''everyone'' takes cover."
*** Bombings by mistake, especially by US aircraft, seeing as there were so many of them, were deadly and common. The highest ranking US general killed in the European Theater of Operations, General [=McNair=], was killed while visiting the front when his observation post was bombed by B-17s by mistake.
** Units engaged in secret operations under cover were always in danger of being attacked by mistake. The ''Doggerbank'', a formerly British merchant ship used by the German navy for covert operations, was sunk by a U-boat mistaking it for a British ship, with the loss of all but one of the crew.
** Another awkward case for the Germans occurred in [[https://en.wikipedia.org/wiki/Operation_Wikinger Operation Wikinger]], a sortie by the Luftwaffe and the Kriegsmarine as a commerce raid. The problem was that neither detachment was coordinated by a single unified command, on account of InterserviceRivalry and plain old RightHandVersusLeftHand ineptitude. What followed was a case where German destroyers were spotted by German aircraft, who in turn spotted the German bombers. The destroyers fired first, taking the Luftwaffe units as hostiles. Convinced that the vessels beneath them were British ships, the Luftwaffe squadrons proceeded to bomb them. The destroyer ''Leberecht Maass'' was hit by a salvo of Luftwaffe bombs and promptly exploded, broke in two, and sank in minutes. In the ensuing mayhem, the destroyer ''Max Schultz'' pulled out of formation to avoid the bombers, wandered in a German minefield, and also promptly exploded, this time with no survivors. Fearing that the loss of the ''Max Schultz'' was due to a British submarine torpedo attack, the destroyer ''Theodor Riedel'' proceeded to fire large numbers of depth charges into the water, which successfully blew up its own rudder. The total loss to the Germans were two destroyers sunk, another damaged, and nearly 600 sailors killed in action, resulting in a decisive British victory. This leads to a rare case of a wartime engagement where one of the belligerent parties was not even present for the battle ''[[WinsByDoingAbsolutelyNothing and won regardless]]''.
** A very awkward battle from Estonia: As it happened, the Soviet Union and Nazi Germany were both invaders. While the Soviets forcefully conscripted Estonians in 1939-40 and in 1944-45, the Nazis only took volunteers in 1940-1942 until in 1943 they conscripted every able-bodied male into the SS, leaving the Soviets with just the old men and the kids coming-of-age[[note]] making these men the only SS men who were not automatically treated with a great deal of suspicion after the war, incidentally, since they were the only conscripts to feature in their fighting formations [[/note]]; either way, there were entire units of Estonians on both sides. During a particularly dark night, one of the Soviet-Estonian companies encountered a Nazi-Estonian company while marching through the forest. Since both sides spoke Estonian, neither unit realized they were marching with the enemy--but when they did, all hell broke loose. Due to low visibility, the soldiers dropped their weapons, grabbed bayonets or knives and then held their weapon in one hand and with the other reached to touch each others' heads under the helmets. This is because the Soviet conscripts had shaven heads while the German army let the volunteers' hair be--so they determined who was friend or foe by haircut. You could say it was the most awkward and largest KnifeFight in military history.
** Operation Husky: 144 C-47s were on approach for a night-time paradrop operation in Sicily but were fired upon first by Allied ships and then ground forces. A German air attack had occurred just minutes before the C-47s were arriving near the island and the naval AA gunners were simply too nervous to think first and shoot later.
** Operation Bodenplatte: 900 German fighters and fighter-bombers were launched in a surprise attack to destroy allied airfields in the Low Countries. The attack had failed with 300 planes and 237 pilots lost. Many of the casualties were caused by the secretive nature of the operation which resulted in much of the German Army and Navy in not being informed of a German Air Offensive which in turn led to many German AA batteries opening fire on their own planes.
** The [[UsefulNotes/BritsWithBattleships Royal Navy cruiser]] HMS ''Sheffield'' was subject to this not once, but ''twice'' during UsefulNotes/WorldWarII. The first time was when she was participating in the hunt for the [[UsefulNotes/NazisWithGnarlyWeapons German battleship]] ''Bismarck''. A squadron of Fairey Swordfish torpedo bombers had been sent to attack the ''Bismarck'', but not been informed of the position of the ''Sheffield'', and attacked the ''Sheffield''. Luckily, the torpedoes had been armed with highly-unreliable magnetic detonators, and most of them exploded prematurely. While the sailors presumably shouted unprintable things at the aviators (one of whom messaged an apology via signal lamp), the ''Sheffield'' bridge staff dryly messaged the HMS ''Ark Royal'' (the aircraft carrier from which the Swordfishes had launched), saying that 1) your planes torpedoed us by mistake, and 2) the torpedoes didn't work. The second occasion was during the [[http://en.wikipedia.org/wiki/Battle_of_the_Barents_Sea Battle of the Barents Sea]], when the ''Sheffield'' was mistaken for the German cruiser ''Admiral Hipper''... by the two destroyers assigned to escort the ''Hipper''. The ''Sheffield'' did not make a similar mistake, and sank one of the German destroyers.
** The Polish submarine ORP Jastrząb ("Hawk") was escorting an Allied convoy to Murmansk when on May 2, 1942 it was attacked by Allied surface ships. Five crew members were killed and 6 others wounded. The submarine was severely damaged and was scuttled at sea. To this day there is dispute among historians as to who was really at fault for the friendly fire incident.
** This was a problem during the Warsaw Uprising. Polish fighters would scavenge German weapons and equipment including helmets and clothing. In the chaos of urban fighting it was often hard to tell whether someone running toward you was a German or a fellow resistance fighter dressed in a German camouflage coat.
** In [=WW2=], there were "natural enemies" that would often attack each other on the flimsiest of excuses. Ships viewed aircraft, submarines, and small torpedo craft as to be shot at until proven otherwise, knowing that their best defense was to engage as early as possible to disrupt an attack. Fighters would view other single-engine aircraft with great suspicion. Submarines thought that anything small with visible guns was an enemy destroyer until it proved otherwise. Torpedo boats tended to see anything that floated as a valid target. Bombers viewed any single engine plane approaching them as a reason to open fire.
** One issue in air-to-air combat in Europe was that the American P-47 Thunderbolt had a very similar profile to the German Messerschmitt Bf 109, making distinguishing between the two difficult under combat conditions.
** Operation Cottage: In August of 1943, a combined force of American and Canadian troops launched an invasion of the Japanese-held island of Kiska. However, inaccurate intelligence meant the Allies didn't know that the Japanese had abandoned the island two weeks earlier, and rough terrain and foggy weather led to friendly fire incidents that resulted in 32 soldiers killed and another 50 wounded.
** The Battle of Los Angeles: In February of 1942, war nerves and a misidentified weather balloon led to US Army anti-aircraft batteries in and around Los Angeles thinking they were under attack by Japanese bombers and firing into the clouds in response. 5 civilians died as an indirect result (3 from car accidents caused by the chaos and 2 from heart attacks), and several buildings and cars were damaged by falling shell fragments.
** This became an issue given the number of captured Allied tanks and tank destroyers that the Germans made use of. There was also an experiment in modifying Panthers to resemble American M-10 Wolverine tank destroyers, including American-looking paint jobs.
* A number of friendly fire incidents have happened in Afghanistan during UsefulNotes/TheWarOnTerror:
** American-on-Canadian: The Tarnak Farm incident of April 2002. A U.S. Air National Guard F-16 mistook Canadian Army soldiers for Taliban fighters with anti-aircraft weapons. The farm had previously been used as a firing range by the Taliban, but was now being used by the Canadians for anti-tank and machine gun exercises. Although denied permission to attack by the controlling [[VoiceWithAnInternetConnection AWACS]], Major Harry Schmidt believed the soldiers on the ground were targeting his flight leader, and bombed them in response. This cost the lives of four soldiers while wounding eight others.
** British/American-on-Afghani: During April 2006, British convoy called in an airstrike from American warplanes on Afghanistan police officers, mistaking them for attacking Taliban forces, killing one and wounding twelve. Note that in this case, the U.S. pilots were attacking as specified by the British, and not making an error of judgment of their own.
** British-on-British: In Sangin Province during August 2006, an RAF Harrier was called in to assist British troops during a firefight with the Taliban. The Harrier strafed the British instead, missing the enemy by 200 meters. This angered Major James Loden of 3 PARA, who called the RAF "Completely incompetent and utterly, utterly useless in protecting ground troops in Afghanistan." Some British paratroopers have even said they prefer American air support to the Royal Air Force.
** American-on-British: In a case of PoorCommunicationKills, one of two American F-15Es called in to support a platoon from 1 R ANGLIAN dropped a bomb on top of the unit, killing three soldiers. The forward air controller in the platoon, Sergeant Mark Perren, was not issued a noise-reduction headset; the platoon was under heavy fire by the Taliban, making it hard to hear radio transmissions. When the F-15E pilot repeated misheard target coordinates for confirmation, Sergeant Perren wound up confirming his own location as the target.
** British-on-Danish: In Helmand Province during September 2007, British soldiers fired Javelin missiles at a unit of Royal Life Guards, killing two of them. The British soldiers had mistakenly identified the Royal Life Guards' camp as a Taliban hideout, and requested permission to attack. The Royal Life Guards, not realizing ''they'' were the ones being targeted, granted permission.
** Dutch-on-Dutch/Afghani: During January 2008 in the Uruzgan Province, a unit of the Dutch Army attacked a composite group of Dutch and Afghan soldiers that they had mistaken for the Taliban. Two Dutch and two Afghani soldiers were killed before the firefight ended.
** American-on-British: In January 2008, two Apaches, one British and one American, were called in to support a unit of Grenadier Guards and Afghan forces fighting the Taliban in the Helmand Province. The British Apache opened fire on the Taliban, while the American Apache attacked the Grenadiers. Only one person was wounded. After the incident, a high ranking British Army officer claimed that in contrast to the UK's full-time professional air forces, most American pilots are merely reservists, implying that this is why British-on-American friendly fire incidents never happen.
** British-on-British: Later that year in July, a British WAH-64 Apache was called in to support a unit from 2 PARA against Taliban fighters. After attacking the Taliban positions, the Apache mistook the 2 PARA unit for more Taliban and opened fire, wounding nine of them.
** German-on-Afghani: In early 2010, a unit of German soldiers arriving at the scene of an earlier firefight where the Taliban had ambushed a bridge-laying and mine-clearing operation encountered Afghan Army soldiers in civilian vehicles. After the Afghanis ignored an order to stop, the Germans fired on them, killing six of the soldiers.
** American-on-Pakistani: In November 2011, a joint 150-man U.S. and Afghani unit came under fire and called in an airstrike. Miscommunication between U.S., NATO, and Pakistani forces led to two Pakistani border posts being destroyed, killing 25 Pakistani soldiers.
** American-on-American: This is what happened to Army Ranger Spc. Pat Tillman in Afghanistan, 2004. Official story: Tillman's unit was ambushed and split in two during a patrol and his section moved ahead to get into a better position to provide support. The other part of the unit mistook the Tillman's section for the enemy and fired on them killing Tillman and an Afghani soldier. Tillman was also a professional football player, a safety for the Arizona Cardinals, making the situation even more delicate for the U.S. Armed Forces. Initially the fact it was friendly fire was covered up. Tillman was portrayed as leading a heroic charge against the enemy. The truth was revealed when Tillman's family got suspicious and started investigating. There is some evidence that Tillman's death was not an accident, as he'd begun to criticize the military and the Afghan war. He had planned to meet with Noam Chomsky, a well-known scholar who's been highly critical of U.S. foreign policy, and possibly run for office after his service.
* The 2022 Ukrainian-Russian war quickly proved to be an ''absolute nightmare'' in this regard. The languages are mutually intelligible(and many Ukrainians speak Russian as a first language anyways), they're ethnically similar, and as former members of the [=USSR=], both sides are using [=AK=]-pattern rifles and derivatives of the various Soviet-era tanks and other combat vehicles. Identification quickly boiled down to colored arm (and head, and leg) bands. The identity issues were shown to full effect in a video that showed a Russian tank roll right up to a group of Ukrainian soldiers, neither side realizing the other's identity, until the tank crew finally twigged and fired at point-blank range.
** Russian soldiers wear white armbands, units from the Russian-backed "separatist" Donetsk and Lushansk "People's republics" red, with some [=VDV=] paratroopers going for duct tape silver. The orange-and-black St. George's ribbon has also been used.
** Ukrainian forces seem to have gone with yellow, blue and green, the first two being the colors of the Ukrainian flag. It has been speculated that yellow is for regular troops, blue for volunteers/[=TDF=], and green for police and/or marines, though it's not actually clear.
** Russian vehicles were painted with white "Z", "V", "O", "X", and "A" markings, the "Z" quickly becoming emblematic of the Russian invasion as a whole and gaining a notoriety all its own as the next best thing to a swastika.
** Ukrainian vehicles tend towards yellow-and-blue stripes, sometimes adding a Ukrainian flag.
* In 1796, Amédée Laharpe, a Swiss general fighting for the French Republic, was mistaken for an enemy officer while conducting a reconnaissance at dusk and killed by his own soldiers. Made even more cruel by the fact that he was condemned to death in his home country for supporting the Revolution, and had to leave everything to serve France.
* Napoleon's Grand Army included Hanoverian battalions, who wore the same red coat as the English did. Most of the casualties among Hanovrians serving in the Peninsula were caused not by the Spanish, Portuguese or English, but by their French allies mistaking them for English. In particular, General Marbot tells the story of a Hanovrian battalion at Fuentes d'Oñoro sent to defend a vital spot... and shot at by both the English and the French who were sent as reinforcements. [[{{Determinator}} They held the position for several hours.]] Similar misfortunes happened to the Saxons whose uniforms looked like those of the Austrian, notably at Wagram.
* Modern GPS based tech used by US and other infantry is partially to prevent this. Specifically, this is for when infantry calls for artillery support and provides their own position as the place to drop artillery on. This has resulted in many deaths, mostly American (because Americans are known for their heavy use of artillery and airstrikes). Today thanks to the GPS tech, a call for fire will result in a challenge from the artillery group of "That's your position!" In the event that the infantry wants the artillery strike or airstrike on their own position (such as if the enemy is on top of them, or if the infantry is retreating and being pursued by the enemy), they can respond "I know what my fucking position is!"
* During the 1980's in brawls between neo-nazi and anti-fascist Skinheads, Anti-fascists would often wear their bomber jackets reversed, as otherwise everyone would be wearing identical clothes and shaved heads.

Sometimes, in combat, it's hard to tell who your friends are.

* In ''Comicbook/TheAvengers'', after Hercules had been rendered comatose, Zeus brought the Avengers to Olympus and attacked them. A figure came to their aid, and Zeus fought him for some time, before he realized it was Hercules, risen from his sick bed to help his friends. Zeus is deeply grieved by his folly.
* The orkish view on friendly fire is seen in ''Comicbook/DeffSkwadron'', when the squad commander of deff skwadron chastises one of his gunners when he baulks at firing into a pitched dogfight where telling who is on which side is impossible. Essentially it boils down to "shoot at everything, and if you hit anything it must obviously belong to the enemy."

* In ''Radio/TheHitchhikersGuideToTheGalaxy'' radio series, Arthur is asked this, to which he sensibly replies, "Do I know you?... Well, without knowing you it's hard to tell. I mean I quite like some people, others, not so much." He later goes on to explain that very few of his friends "have piercing red eyes, black armour, and laser rifles."

** Scorch, which destroys the highest unit(s) on the playing field is the prime offender of this. It's gotten to the point that there are message board's dedicated to explaining that if the highest unit is on your side it will be destroyed. To a lesser extent this applies to epidemic which targets all of the lowest unit(s).

* ''Videogame/ChivalryMedievalWarfare'' has serious problems with this, mostly because all battles eventually turn into multi-man melees with archers firing into the fray. And when you swing any sort of weapon into a fray that size, you're eventually going to chop your ally's head off by accident. Archers don't have it any better, and unless you're really good a sizeable portion of your arrows will end up adorning your pals. Even with proper caution taken it's very, very hard to avoid decking someone on your side during any battle bigger than a three-on-two.

* ''Videogame/{{MORDHAU}}'', being a spiritual successor to ''Chivalry'', would naturally have its share.

* ''Videogame/DeepRockGalactic:'' While it's easy enough to tell the dwarves apart from any enemies, when fighting against absurdly huge hordes of bugs in tight quarters does inevitably lead to some friendly fire incidents. Some weapons, like the Engineer's Grenade Launcher and ''especially'' the Driller's Satchel Charge naturally have more problems, due to explosion radius and the usual panic in which they're tossed out. At least there's perks to mitigate friendly fire damage, though the dwarves themselves will still get pissed.

* The rules of {{heraldry}} exist to avert this trope.

* ''Artificial Condition''. Twice when [[Literature/TheMurderbotDiaries Murderbot]] goes into action one of the men he's fighting accidentally kills another in the confusion. Then for a RuleOfThrees Murderbot uses their boss as a BulletproofHumanShield against gunfire from her own bodyguard.

* In ''Anime/MobileSuitGundamWing'', the five Gundam pilots start out wary of each other and sometimes end up fighting among themselves after destroying their mutual enemy. None of them were told by their handlers that there would be others like them, so the HeelFaceTurn they all had concerning the objective of their mission prior to launch made them into each other's potential enemies. Unlike [[{{Fanon}} what the fandom would have you believe]], they don't come together as a five-man team until near the end of the series, but they do often work in pairs of varying combinations once the misunderstandings are cleared up.

* This happens in ''Franchise/StarWarsLegends'' novels as the Galactic Civil War progresses, particularly in works like the ''Literature/XWingSeries''. Due to VehicularTurnabout, the Rebels/New Republic end up using an increasing amount of Imperial military hardware, from captured Star Destroyers to [[MookMobile TIE Fighters]] (though in the latter case the Rebels try to put as many DeflectorShields on the starfighters as possible). So veteran pilots get to deal with lingering nervousness as they approach a friendly Star Destroyer, and in some battles squadron leaders have to tell their pilots not to take a snap-shot at any TIE until their targeting computer confirms it's an enemy. Wraith Squadron in particular, due to their success with TheInfiltration of enemy forces, has a few close calls when an X-Wing pilot sees the TIE in their crosshairs flip from a red to blue target.