A combat move in which a heroic melee fighter, taking aim at an opponent in front of him, swings a large melee weapon over his head and—accidentally or maybe intentionally—hits an enemy standing behind him, taking him out. Usually this is followed by landing a hit on the enemy in front immediately afterwards (what the fighter wanted to do in the first place).
This comes in handy when the hero is outnumbered in a fight and the adversaries do not practice Mook Chivalry, or when a sneaky attacker is about to stab the hero In the Back while he is distracted by the enemy in front of him.
The Dangerous Backswing is not always lethal. Especially there is the comedy variant in which an overzealous fighter does not realize that his mighty swings pose a threat to his own allies standing behind him, and the very companions he means to protect only narrowly dodge possibly lethal hits or else collect some bumps to the head.
Overlaps with Badass Back. Compare Spin Attack, an alternative way to deal with such a situation. If the backswing hits an ally, it's a case of Friendly Fire. Collateral Damage is basically the missile weapon equivalent. Compare and contrast Offhand Backhand, where the character is perfectly aware of the person behind them and clobbers them without looking regardless of whether they are currently facing a threat frontal. Compare Plank Gag, Rod And Reel Repurposed and Deadly Dodging.
- In 101 Dalmatians, Horace accidentally bonks Jasper in the head with a club.
- The Sword in the Stone: As Sir Ector raises his sword over his head to attack the enchanted dishes animated by Merlin's magic, he strikes his son Kay in the head with the backswing. Fortunately for Kay, the blade simply bonks him instead of cutting him. (This scene is Recycled Animation from the scene in One Hundred and One Dalmatians in which Horace bonks Jasper in the head with a club.)
- In Condorman our erstwhile hero, when confronted by a bunch of thugs, grabs his briefcase and swings it back so he can launch it forward at the thug in front in him, only to clobber a thug sneaking up behind him in the face.
- Raiders of the Lost Ark: During the street fight in Cairo, one of the Mooks accidentally hits his comrade when he winds up to hit Indy with a piece of wood.
- In Kung Fu Hustle, Sing and Bone try to throw knives at the landlady, but keep hurting Sing by accident. Bone tries to throw by swinging his arm back and hurling, but stabs Sing instead. Then when they're noticed, Bone lifts a box to throw, not realizing that it's full of snakes and he just dropped a bunch of angry snakes all over Sing.
- In the 1979 Disney comedy A Spaceman in King Arthur's Court, as Sir Gawain turns to open a door he gets pinned to it with a hurled spear. King Arthur goes to remove the spear while lecturing him on never turning your back on the enemy, not noticing the enemy knight sneaking up behind him until he yanks it out, knocking down the knight with the butt of the shaft. Then Merlin tries to sneak up and hit the off switch on the neck of the android Hermes; our hero sees what he's doing and sings the US national anthem, causing the android to salute and knock Merlin aside.
- The Dana Girls book "The Mystery of the Locked Room" starts with one of the girls accidentally hitting a man on the head with a tennis racket, as she was about to demonstrate a strike to her sister.
- Heimskringla: When, in the reign of Harald Gilli, a Wendish raiding army sacks Konungahella, a local farmer called Ölvir Big Mouth rushes bravely but inconsiderately at the invaders and finds himself surrounded by eight Wendish raiders. Ölvir swings his battle-axe over his head so that "the foremost point of the axe-blade struck the one that was behind him under the throat so that it cut his jaw and windpipe in two, and he fell over backwards". Then [Ölvir] swings the axe forwards at the man standing in front of him and "strikes [him] on the head and split him down to the shoulders." Ultimately Ölvir is severely wounded but kills six of the attackers, with two running away.
- Njal's Saga: When Kári and Thorgeir Skorargeir attack the sons of Sigfús, Thorgeir rushes at Thorkel Sigfússon just as one of Thorkel's companions runs up at Thorgeir from behind. Before the man can strike at Thorgeir, Thorgeir swings his battle-axe with both hands and "drove the axe-hammer into the head of this man who stood behind him, so that his skull was shattered to bits." Then Thorgeir lets the axe come down forward on Thorkel and cuts off Thorkel's arm.
- The Saga of the People of Vatnsdal: Ingolf Thorsteinsson, who carries the sword Aettartangi, with one supporter picks a fight with a gang of eighteen outlaws. The outlaws attack from all sides, but Ingolf swings Aettartangi so that "the sword fell on the head of the man standing behind him so that he met his death, and it delivered a death blow to the man standing in front and thus Ingolf killed them both with a single blow."
- The Saga of Hrómund Gripsson: Hrómund's enemy Helgi wins all battles because of his mistress Lara, a shape-changing witch who assists her lover in battle casting spells while flying over the battlefield in the shape of a swan. In Hrómund's and Helgi's last confrontation, Helgi swings his sword at Hrómund while Lara soars overhead and accidentally cuts off Lara's leg, which kills her. Without her magic to protect Helgi, Hrómund can finally kill him. A rare example of the "friendly fire" version Played for Drama.
- In the song "Never Split the Party" by Emerald Rose (a satirical recounting of a Dungeons & Dragons dungeon crawl), the player characters have to dodge the cleric's backswing, implying that they're trying to avoid damage from Friendly Fire.
The cleric swung his holy club, some orcish skulls to break
We tried to dodge his backswing as we pondered our mistake
- Get Amped: The Skull Bardiche accessory takes the form of a large axe. It is so heavy that, when you do an upward swing move with it, the axe smashes down to the user's back, hitting the enemies on the user's back as well.
- A lot of bosses in Dark Souls swing their (giant) weapons in very wide arcs, so it is quite possible to get killed by them even when approaching them from behind while they attack someone (e.g. a summoned ally) in front of them, simply because the strike either starts or ends well behind their back.
- Chivalry: Medieval Warfare, MORDHAU and other such games that put an emphasis on accurate melee weapon combat have a slightly different version of this as a feature; the backswing of the weapon might not touch you, but the actual swing will begin there and hurt like hell, giving you only a half-second more to react than usual. Exploiting this usually becomes fundamental in the metagame.
- Exploitable in Castlevania: Aria of Sorrow with the Red Minotaur soul. This soul swings a giant blade back before swinging it forwards in a full 360 degree arc, so it's possible to hit an enemy twice by facing away from them and then swinging.
- In the Tom and Jerry short "The Truce Hurts", Tom, Jerry and Butch the bulldog are having a three-way battle, in the course of which Tom repeatedly whacks Jerry with a frying pan; Butch, who is standing behind Tom vainly trying to hit him with a baseball bat, gets hit on the head by Tom's frying pan with every of Tom's swings, without Tom even noticing. This repeats no less than seven times in a row.
- Disenchantment, episode #5: "Faster, Princess! Kill! Kill!": Trapped in the dark cellar of Hansel's and Gretel's gingerbread house of horrors, Bean is facing Hansel who advances on her with a pitchfork, while Gretel is creeping up behind her back unseen. As Bean swings a double-bladed axe over her head, intending to strike at Hansel, she accidentally kills Gretel by hitting her in the head, then strikes at Hansel, killing him too.
- In the Looney Tunes Cartoons short, "Funeral For a Fudd" Elmer pretends to be dying while using an unconvincing dummy of himself to lure Bugs out of his rabbit hole; Bugs pretends to fall for it and while using a defibrillator on the dummy, Elmer gets shocked repeatedly while Bugs backswings the paddles (obviously not on accident).
- Megas XLR: While the team is fighting off the latest alien threat, Jamie prepares to attack with a baseball bat but bonks Kiva unconscious on the backswing. When she comes to, he claims that the enemy knocked her out and that he defended her...but then a recording of what actually happened gets played on loop, angering Kiva.
- A variant happens in The Prince and the Pauper. Goofy, disguised as the executioner to save the Prince and Donald from the castle dungeons, slipped on a water bucket and accidentally threw his axe at the weasel guard. When Goofy pulls the axe off the wall, the bladed end breaks off and clangs the weasel behind him on the head.
- In The Simpsons Treehouse of Horror IX short, "The Terror of Tiny Toon", when Bart and Lisa are sucked into an Itchy and Scratchy cartoon where the two titular characters are trying to kill them, while Itchy is trying to attack Bart and Lisa with a chainsaw, his backswing ends up accidentally chopping off Scratchy's arms while he's driving a police car.
Itchy: Sorry.Scratchy: It happens. (grabs the steering wheel with his mouth)
- This is a real risk of using tools like machetes.
- Same goes for fishing rods. A careless cast can strike someone with the sinker or snag them with the hook. For people dumb enough to stand behind the caster, there's also a good chance they'll get thwacked by their arms or the rod itself during the backswing.