%% This list of examples has been alphabetized. Please add your example in the proper place. Thanks!
A Keystone Army[[note]]A ''keystone'' is the wedge-shaped stone piece at the apex of a masonry vault or arch, which is the final piece placed during construction and locks all the stones into position, allowing the arch to bear weight. If it is removed, the whole structure falls, AndThatsTerrible. A lot of people do know what a keystone is, but its usage in architecture has dwindled with steel frames.[[/note]] is an invasion force or army that's [[NighInvulnerability seemingly unstoppable]], except for [[AttackItsWeakPoint one particular weakness]] [[AchillesHeel in the form of a well protected but very fragile component]]. It can be an individual soldier, an object or whatever, but if you destroy or tamper with it, [[InstantWinCondition the entire army is immediately disabled]]. This plot device is handy as it allows a [[FiveManBand handful of heroes]] to win the war without having to depict them fighting off the entire enemy force. Just a daring raid on the enemy's stronghold and BAM! Evil is defeated. It also allows otherwise unstoppable foes to be suddenly stopped dead in their tracks.

General forms include having the MacGuffin-weakness be the HiveQueen of an enemy HiveMind, the sole [[PowerSource source]] of all the enemies' powers, or the [[FantasticFragility lone connection]] to AnotherDimension. Just like a real keystone, once it's destroyed, the rest falls apart.

Of course, [[NoPlansNoPrototypeNoBackup no one ever considered that someone would aim at their army's one weakness]]. After all, it would be rather anticlimactic to destroy the KillerRobot's central control but have a backup one come online in another location.

BeePeople are likely to be a Keystone Army if they have a HiveQueen, and as such trashing it is a good way to win the BugWar. Another common Keystone Army simply replaces the insects with {{Killer Robot}}s or GreyGoo and the Hive Mind with a MasterComputer or evil [[AIIsACrapshoot AI]], and yet another popular variation has an EvilSorcerer whose (often [[TheUndead Undead]], [[MindControl Mind Controlled]] or [[LegionsOfHell Demonic]]) minions will cease to be a problem due to NoOntologicalInertia [[ShootTheMageFirst upon his death/defeat/distraction]]. An army of monsters may be defeated by killing the MonsterProgenitor. [[EasilyThwartedAlienInvasion Easily Thwarted Alien Invasions]] often employs such armies. WeCannotGoOnWithoutYou is a case of the player character of a video game being the keystone in their party's army.

Despite the name, only occasionally is the vital component a CosmicKeystone. A type of InstantWinCondition. See also DecapitatedArmy, for when the keystone is the leader. StraightForTheCommander exploits this trope. The armed forces equivalent of a TerminallyDependentSociety. See also FantasticFragility. Compare UntouchableUntilTagged, when individual NighInvulnerable fighters get mobbed after an unlucky hit.

Similar, but not to be confused with the ''[[Creator/KeystoneStudios Keystone Kops]]''. No relation to UsefulNotes/{{Pennsylvania}}'s[[note]]which is known as "The Keystone State"[[/note]] National Guard.


[[folder:Anime and Manga]]
* In ''LightNovel/BakaAndTestSummonTheBeasts'', during the summoner test wars, taking out the class rep is an InstantWinCondition. Naturally the students usually try to protect their leader, but sometimes the opposing class will bait them somehow and lure them away so as to weaken the rep's defenses and take them out.
* ''Manga/{{Naruto}}'':
** The army of [[spoiler:ninja resurrected by [[{{Necromancer}} Kabuto]]]] was controlled and created by his technique, and thus can be stopped by defeating him. However, just killing him won't [[NoOntologicalInertia get rid of it]]; he has to actually be forced to stop it.
** The first ''Naruto Shippuden'' movie features a nigh-invulnerable terracotta army that is animated by an EldritchAbomination type being called Mouryu. The only practical way to stop it is by sealing this creature, which is in itself a pretty tall order once its soul and body have reunited. Which, in a surprising moment of savvy, is why they sealed the soul & body in two different places. Mouryu, unfortunately, has shades of AsLongAsThereIsEvil going on.
* ''Anime/SpaceBattleshipYamato 2''. Desslok's flagship has a brigade of robots which Kodai (Wildstar) defeats by blowing up their central computer.
* In ''Anime/TengenToppaGurrenLagann'', as soon as Simon beats Lordgenome, all of the Beastmen's Gunmen instantly power down.

[[folder:Comic Books]]
* In a 1970's {{Comicbook/Avengers}}, ComicBook/{{Thanos}}' space fleet is attacking Earth. It turns out that all of the multivaried aliens in the fleet are depending on a single gizmo on one ship to translate for them so they can understand each other. The Avengers destroy it, and then win fairly easily. Somewhat justified when it turns out that Thanos [[XanatosGambit arranged the whole thing]] as a distraction from his ''real'' evil plan, and didn't especially care whether the space fleet succeeded or not.
* ''Comicbook/{{Supergirl}}'': In the ''Comicbook/RedDaughterOfKrypton'' storyline, Supergirl faced off against the Diasporans -an alien space force that had devastated several planets and wiped out their inhabitants-. However their leader was being mind-controlled, so the whole army surrendered once Supergirl defeated him.
* In the final run of Gail Simone's Franchise/WonderWoman run, she faces off against the Citizenry, a genocidal military force so fearsome that they eat [[Franchise/GreenLantern Green Lanterns]] for breakfast. Fortunately, their self-justification is based on their own strength, so when Wonder Woman defeats their leader said leader loses all status and Diana's able to order them to stand down.
* ''ComicBook/JudgeDredd'': In the ''Judgment Day'' arc, the villain Sabbat's zombie army is entirely dependent on his continued control to function. The Judges of the world's Mega Cities eventually assemble a strike team to take out Sabbat in a last-ditch effort to prevent the Earth from being destroyed completely.

[[folder:Fan Works]]
* The square miles of regenerating undead army in ''Fanfic/WithStringsAttached'' are powered by the Heart of Evil, in a ruined city miles away from where the four and Jim Hunter are surrounded. Having been made a little stupid by rage, and never having grasped just how effective Ringo is at finding stuff, Jeft never imagined that the little band could escape their encirclement, get to the city, go straight to the Heart of Evil, semi-accidentally defeat its powerful guardians, and destroy it, which instantly destroyed all the undead. Which ''really'' pissed Jeft off, since not only did he not punish Jim Hunter for his HeelFaceTurn and the four for instigating it, but that heart was ''expensive''.
* In the ''WesternAnimation/TheLegendOfKorra'' fanfic [[FanFic/BookFiveLegends Book Five: Legends]], when the bender animating the walking dead men is rendered unconscious, their animation fails and they fall like dominos. Naturally, this is incorporated into the defense of Republic City in the final chapters.
* ''FanFic/AShadowOfTheTitans'' has an example at the climax of the HIVE Arc: [[spoiler: the Shadowkhan's keystone isn't Tarakudo, but the Queen/Kagehime, who has the fragments of the Red Mask [[ClingyMacGuffin in her]]. When they and Tarakudo's chi are expelled from her body, the Shadowkhan are [[SealedEvilInACan re-sealed]].]]
* ''FanFic/DungeonKeeperAmi'': The Dungeon Hearts are the Keystones of a Dungeon Keeper's army, as killing the heart banishes the Keeper.

[[folder:Films -- Animated]]
* ''WesternAnimation/TheLegoMovie'' mimics ''Film/{{The Avengers|2012}}'' and ''Film/ThePhantomMenace'' by having the Micromanagers drop dead with the destruction of the SupervillainLair.

[[folder:Films -- Live-Action]]
* ''Film/{{The Avengers|2012}}''. Destroying the mothership causes all the aliens to drop dead. In the DVDCommentary, Creator/JossWhedon admits that he hated having to resort to this trope, [[EnforcedTrope but it was]] [[NecessaryWeasel necessary]] to give the heroes a clear victory instead of battling for seventeen more hours of cleanup.
** Notably averted in the sequel - all of Ultron's drones and copies need to be destroyed, not just the primary, [[spoiler:vibranium enhanced]] copy, because any of them is a complete copy of Ultron who can start over. And there's no shortcut or self destruct mechanism to get them all at once either.
* Played with in ''Film/BattleLosAngeles''. The alien invaders are ferocious opponents on the ground and are driving back the US military from Los Angeles and other coastal battlefields even before their drone support shows up overhead. The drones themselves are controlled from a large command center that, when taken out, causes the drones to crash and the United States military to regain air superiority over Los Angeles, but the war is far from over and the aliens remain a tenacious force on the ground.
* On two levels in ''Film/EdgeOfTomorrow''. Every Mimic force comes with an Alpha. If that dies, the Omega [[spoiler:resets everything with foreknowledge of how things went down in the last loop]], adapting until the Mimics win. Killing the Omega, however, stops all the Mimics.
* In ''Film/TheGreatWall'', killing the Tao Tieh queen causes all the other Tao Tieh to become paralyzed.
* Done in ''Film/HellboyIITheGoldenArmy'', where the [[MacGuffin demon crown]] is the keystone.
* In ''Film/IndependenceDay'', the alien ships are rendered shieldless through a virus uploaded to the mothership, which apparently maintains a constant data link with both the motherships and the fighters. Despite claims that this would only last a few minutes, they never get their shields back. This is a slight twist as the aliens are still perfectly healthy and their technology (other than the shielding) is still functioning, but they're much less of a threat without it.
** Reused in ''Film/IndependenceDayResurgence'' where [[spoiler: after killing the alien queen, all of the aliens immediately drop dead and the mothership leaves Earth.]]
* The rogue robots in ''Film/IRobot''. [[spoiler:Since VIKI was remotely distorting their programming to make them hostile to humans, they immediately became docile upon her defeat.]]
* ''Film/InTheNameOfTheKing: A VideoGame/DungeonSiege Tale'' has the Krug, formerly mindless beasts who have been magically uplifted by [[EvilSorcerer Gallian]] to serve as his army. Still mostly beasts, they fight using WeHaveReserves tactics. As soon as Farmer slits Gallian's throat, the Krug stop and, after standing around in confusion, drop their weapons and wander off.
* In ''Film/KingsmanTheSecretService'', Valentine's entire private army and his powerful co-conspirators are taken out in a single keystroke [[spoiler:due to the implants that kept them safe also doubling as a miniature explosive and Merlin's hacking enabling him to activate them all at once]].
* Arguably in ''Film/TheLastStarfighter'', the Xodan Command Ship's communications turret. It is what allows the entire armada of space fighters to coordinate. Without it, they're not as effective and taken out quickly with a MacrossMissileMassacre thanks to the Death Blossom.
* In ''Film/TheLordOfTheRings'' movies, destroying the One Ring destroys Sauron (this at least is justified, as it's a SoulJar), which causes his armies to flee while Mordor suffers what can only be called a [[LoadBearingBoss catastrophic geographical failure]].
* ''Film/TheMummyReturns'': The unending army of Anubis turns to dust when the title's Scorpion King is killed and ordered to take his army with him. Justified, because whoever kills the SK, [[YouKillItYouBoughtIt becomes the legitimate master of the army]]. The good army is just preventing the anubites from getting out into the world, they knew they couldn't win on their own.
* ''Film/{{Oblivion 2013}}'' : [[spoiler: After the Tet gets blown up, the drones immediately deactivate.]]
* ''Franchise/PiratesOfTheCaribbean:''
** ''Film/PiratesOfTheCaribbeanTheCurseOfTheBlackPearl'': The curse which rendered the crew of the Black Pearl [[{{Immortality}} immortal and unstoppable]]. Jack and Will break the curse while the crew is in the middle of a climactic battle with Norrington's men, and the second that the pirates realize that their key advantage is lost, they surrender.
** ''Film/PiratesOfTheCaribbeanAtWorldsEnd'': The ''enormous'' Imperial Armada Beckett brought with him to annihilate the pirates: they all turn tail and run when the ''Endeavour'' is sunk, despite it being heavily implied that they vastly outnumber the entire pirate fleet. May simply be a case of LazyBackup. On the other hand, they were up against the Black Pearl, which was pretty infamous at the time for her actions, as well as the Flying Dutchman, all at once. Especially the Dutchman, who would probably have made it a curbstomp battle given how everyone keeps saying "Control the Dutchman, control the seas."
* The Borg Queen and her Borg in ''Film/StarTrekFirstContact'' (at least, those Borg who survived the engine coolant spill)
** And done in "The Best of Both Worlds" when the ''Enterprise'' rescues Picard/Locutus, who they use to destroy the Borg Cube...by telling them all to "go to sleep".
* ''Franchise/StarWars'':
** ''Film/ThePhantomMenace'':
*** Once Anakin blows up the Trade Federation's control ship, the droid army shuts down.
*** A less literal version with the Gungan army; they turn and flee as soon as their shield generator is destroyed. Justified, because the Trade Federation army had brought tanks to the battle, and with the shield down they could move in. And do. They also had no reason to stay once the enemy was fully committed, since the battle was only a diversion in any case.
** This was subverted in cut content of ''Film/AttackOfTheClones''; the Jedi blow up the droid control ship, shutting the droids down en-mass, [[ItOnlyWorksOnce only for them to all power up again seconds later when their new onboard backup systems boot up.]]
** ''Film/RevengeOfTheSith'': After Anakin kills the Seperatist leaders, he is able to shut down the entire droid army with the push of a button. Of course since Palpatine was behind both sides of the war the entire time, he made sure the droids were built with this flaw so that he could end the war instantly once he had accomplished his goals.
** The earliest ''Franchise/StarWars'' example is of course [[Film/ANewHope the original]], with the Death Star's [[AchillesHeel exhaust port]]. Reused in ''Film/ReturnOfTheJedi'' with the Death Star II's main reactor, not to mention Palpatine dying with it. These both are arguably subversions, however, given that the Empire, in the original ExpandedUniverse, kicked the rebels off the moon shortly after the Battle of Yavin and that the civil war still officially went on for another fifteen years after Endor and ended in a draw. In the new EU, on the other hand, the trope is present but [[DownplayedTrope downplayed.]] The rebels kicked the Empire off the moon instead and the war still carried on, but only for about a year. The loss of centralized leadership and the massive financial losses the Empire suffered, not to mention a vast increase in support for the rebellion, all did the Empire in as it succumbed to infighting. So while the act of destroying the second Death Star and killing the Emperor did not magically make the Empire vanish, it did pretty much decide the course of the war in the Rebellion's favor. It helped that the Emperor had set the system up this way deliberately as an attempt at VetinariJobSecurity, and left orders in the wake of his death to devastate loyalist worlds out of sheer spite.
* In the ''Film/TotalRecall2012'' remake, the BigBad is making an army of robots to take over the only other habitable area in the world. The protagonist finds out about a shutdown code for the army buried in his memories. When LaResistance leader tries to access the memory, this triggers a hidden code that allows the BigBad to find him. Also played straight when the protagonist destroys [[spoiler:the Fall, a gravity elevator from Europe to Australia, destroying the robots aboard]].

* Justified in ''Literature/{{Animorphs}}''. When the heroes take control of the Yeerk Pool Ship and Visser One, the Yeerk general, it provides the Andalite army with comprehensive intelligence on Yeerk military, that allows them to turn tides in the war and defeat the Yeerk Empire.
* [[ZigZaggingTrope Zig-zagged]] in ''Literature/TheChroniclesOfThomasCovenant'', specifically ''The Power that Preserves''. [[SupportingLeader Lord Mhoram]] thinks that by killing [[TheDragon Satansfist]], the commander of the army besieging Revelstone, he'll be able to rout the entire army. It doesn't work, because the [[EvilSorcerer ur-vile loremasters]] take command immediately upon Satansfists death and restore order. But when Covenant defeats [[BigBad Lord Foul]], the ur-viles sense it and decide to call it quits, and the whole army crumbles.
* In ''Literature/CodexAlera'' without their Queen the Vord are just animals. Dangerous ones, but manageable. Although normally queens possess the ability to give birth to new subsidiary queens, so killing one may rout the Vord in the area, but won't destroy their threat. The Vord Queen in Alera explicitly says [[spoiler:she blocked this ability in all other Vord since other Queens immediately tried to kill her]], leaving one primary keystone target.
** Ultimately, though, this trope is averted: after [[spoiler: The original Queen dies]], the Vord revert to their simple, individualistic natures, but because they're arranged in a massively tight formation charging into the Aleran defenses, they still have no choice but to keep attacking. Although the battle is made easier since the Vord near the back will desert and some others might resort to attacking each other, the Aleran forces still have to fight on for several hours after their victory is assured.
* The Buggers and their Queen from ''Literature/EndersGame''. Somewhat subverted in that the Buggers actually know that this is their weakness and actively hide the Queen among the rest of the ships. It takes a genius tactician like Ender to figure out which one is the Queen ship, and even he can't do it in the middle of combat. On top of that, the Queen usually isn't even with her troops, being capable of instantaneous communication from halfway across the galaxy. As a result, Ender ends up having to wipe out whole fleets at a time.
** It's played straight in the narration of the past [[BugWar Bug Wars]], with the [[JustifiedTrope justification]] that [[spoiler:the [[HiveMind Buggers]] only saw killing a HiveQueen as killing, which was part of the reason for Humanity's fear and hatred of the species; when they happened upon a human colony, they dismantled our technology to see how it worked - ''after'' they "dismantled" the ''colonists'' to see how '''they''' worked. They didn't understand how much that would piss us off any more than they could comprehend that we would kill a sentient queen, rather than the nonsentient workers.]] They've learned.
* In ''[[Literature/SpaceMarineBattles Fall of Damnos]]'', both sides think that the other is this, but only one's right.
** The Necron warriors become stilted and repetitive when there's no Lord to command them. Sicarius spends the entire book trying to exploit this fact.
** Sicarius' target, the Undying, believes the same of the Ultramarines and thus goes straight for Sicarius. Unfortunately for him, humans aren't Necrons.
* In the ''Literature/HeraldsOfValdemar'' series, the kingdom of Hardorn has waged two wars against Valdemar with forces composed of a few mages and loyal generals and a mass of mind-controlled conscripted troops. In both cases, killing the mage freed the soldiers, who then turned on their generals and ripped them to pieces.
* In ''[[Literature/InheritanceCycle Eragon]]'', the [[OurOrcsAreDifferent Urgal]] army in Farthen Dur was routed when Eragon took out [[TheDragon Durza]], thus breaking his mind control over them.
* In Creator/JRRTolkien's ''Literature/TheLordOfTheRings'', the destruction of the Ring [[DecapitatedArmy kills Sauron]], which confuses and thus incapacitates the parts of his armies which were more directly controlled by his will (e.g. the orcs), which makes them easy game; the not-magically-controlled human armies had various natural reactions, some surrendering and some keeping on fighting.
** On a smaller scale, Sauron's human army from Harad are routed when their chieftain is slain by King Théoden.
* In the post-Apocalypse novel ''Literature/{{Malevil}}'', depending on a Keystone Army becomes the plan of attack near the end of the novel. [[spoiler:The BiggerBad is marching his army toward the hero's castle, he rules his men with fear and bad luck has cost him his two best lieutenants. If they can kill him and his last second-in-command then his army should disband. They have to succeed because while he can't take the castle in a single battle, they won't be able to win a prolonged guerrilla war against him.]]
* The Cauldron-Born (an army of undead) from ''Literature/TheChroniclesOfPrydain'' rampage without end until [[spoiler:Taran recovers the [[InfinityPlusOneSword Enchanted Sword]], Dyrnwyn, and stabs one with it - instantly destroying '''all''' of them]].
* In the ''Starfire'' series, the alien Bugs (big spider monsters with insane numbers on their side) are all but invulnerable... until they are stopped by a tiny flaw in their evolution: kill enough of them at once and the others feel the pain of their deaths. Kind of like a whole race of Obi Wan Kenobis, all feeling a billion voices crying out in pain only to be silenced. Only these guys all have a fatal stroke when they feel them.
* Averted in ''Literature/TheRadiantDawn''. [[spoiler:It isn't Aaron's death that stops the undead, but Stacie's surrender. Knowing that she can't summon Tyadrig without Aaron, she decides to let the heroes have an actual victory instead of a pyrrhic one and siphons the magic from all the undead.]]
* In the ''Franchise/StarWarsLegends'' series ''Literature/TheThrawnTrilogy'', Grand Admiral Thrawn has a theory that the Emperor used his Force abilities to augment the performance and coordination of his troops until they were, unknowingly, completely dependent on him, and as a result became shockingly inept and amateurish after the Emperor's death. Thrawn's NumberTwo, Captain Pellaeon, refuses to accept this... until he sees a rise in troop performance similar to Thrawn's predictions after [[TheRemnant the Imperial Remnant]] allies with a [[FallenHero Fallen Jedi]] and uses said Jedi's abilities to coordinate themselves in battle.
-->'''Pellaeon:''' The Emperor was not directing the battle. Not in any way. I was there, AdmiralóI know.\\
'''Thrawn:''' Yes, Captain, you were there. And it's time you gave up your blindfold and faced the truth, no matter how bitter you find it. You had no real fighting spirit of your own anymoreónone of you in the Imperial Fleet did. It was the Emperor's will that drove you; the Emperor's mind that provided you with strength and resolve and efficiency. You were as dependent on that presence as if you were all borg-implanted into a combat computer.\\
'''Pellaeon:''' That's not true. It can't be. We fought on after his death.\\
'''Thrawn:''' Yes. You fought on. Like cadets.
* In the ''Literature/WarriorCats'' book ''Firestar's Quest'', there's a large horde of HiveMind rats. Once Firestar kills the leader, they're too confused to fight because they have absolutely no idea what to do now, and those who aren't killed scatter.
* The [[OurOrcsAreDifferent Trollocs]] in ''Literature/TheWheelOfTime'' series are the vicious and terrifying foot soldiers of the Shadow. Unfortunately, though they are violent and bloodthirsty, they are also, by nature, selfish and lazy. The only way they can be utilized effectively as a military force is by having Myrdraal control them with a mental link and the use of fear. This makes them a great danger, but if the Myrdraal dies, so do all the Trollocs linked to it. ({{Downplayed}} in that each Myrddraal officer is only linked to a platoon or at most a company - you need to kill all the Myrddraal to take out the whole army, and they won't all be in one place.)
* ''Literature/WindOnFire'' series: In ''The Wind Singer'', the [[TheHorde Zars]] are known for being unbeatable due to having infinite numbers. [[spoiler: The titular Wind Singer's music, however, [[DePower strips off their magic]] and [[NoImmortalInertia makes them age]].]]
* Inverted in ''{{Literature/Animorphs}}''. The Helmacrons are a hive species who kill their queen upon enthroning her so she becomes "infallible". In their case, their hive mind means that none of them can really die, so killing the queen has the opposite effect of spreading her own consciousness rather than eliminating all of theirs.

[[folder:Live Action TV]]
* ''Series/DoctorWho'':
** In the episode "[[http://tvtropes.org/pmwiki/pmwiki.php/Recap/DoctorWhoNSS2E13Doomsday Doomsday]]", when the space-time rift that pulled through an army of Cybermen and a ship full of Daleks is closed, it starts to suck them back in.
** In "The Age of Steel", the Cybermen are stopped when the program preventing them from feeling emotions is disabled - upon realizing the nature of the BodyHorror they've become, the Cybermen ''kill themselves en masse''.
** The Ood from "[[Recap/DoctorWhoNSS4E3PlanetOfTheOod Planet of the Ood]]" have a form of hive mind. Destroying it would presumably kill all the Oods. The subversion being that the BigBad tries to destroy it while the Doctor has to save it.
* ''Series/GameOfThrones'': By Season 7, Daenerys' court are clearly the most powerful faction on the show (with the possible exception of the White Walkers) once they are allied with the Starks to defeat the Northern threat. However, multiple characters note that if Daenerys herself (the only one capable of controlling her dragons and commanding the Dothraki) is killed, her alliance will crumble instantly. Tyrion advises against Daenerys fighting in the field for this very reason. In episode 4 of Season 7, Jaime Lannister demonstrates Daenerys' importance when he initiates a suicidal charge against her for the chance to end the war between Daenerys's faction and the Lannisters.
* The armies of Vortigern in the 1998 ''[[Series/{{Merlin1998}} Merlin]]'' series. [[spoiler:Once Merlin disposes of their king, they cease fighting, and Vortigern's rival Uther is shortly thereafter crowned king.]]
* In ''Franchise/StarTrek'', as soon as the bridge of a starship is captured, the entire rest of the ship is implied to surrender. This is {{Handwave}}d by WordOfGod saying that capturing the bridge allows the boarders to use the ship's own anti-intruder measures against the rest of the crew. It's still a bit ridiculous seeing the thousand man crew of the ''Enterprise'' being defeated by three Ferengi.
* ''Series/StrangerThings'': Since the [[EldritchAbomination Mind Flayer]] serves as the core of the HiveMind connecting everything under its control, when the [[HellGate gate]] to its home in the [[EldritchLocation Upside Down]] is forced shut, the Demodogs and MeatMoss it was invading Hawkins with all drop dead and dissolve.

* In the rock opera by Music/TheProtomen called "The Father of Death" Dr. Wily, tricks Dr. Light into committing terrorist acts and sending Joe to destroy his tower. Turns out Wily had a second control tower located in a fortress and he was only waiting for Dr. Light's attack to give him an excuse to deploy his robot army and declare martial law.

[[folder:Tabletop RPG]]
* A ''TabletopGame/{{BattleTech}}'' example would be the initial Clan invasion. When a lucky hit takes out their supreme war leader, the entire hitherto unstoppable Clan advance practically grinds to a halt for months as their Khans return to their distant homeworld cluster to elect a new one. (Choosing a new ilKhan requires a vote by ''all'' the Khans, not just the few actually running the invasion at the time.)
* In ''TabletopGame/{{Chess}}'', the king is all that matters.
** The same goes for the Japanese game of Shogi, which is not unlike Chess.
* This is a classic trope for fantasy [=RPGs=] like ''TabletopGame/DungeonsAndDragons''. Often times the AlwaysChaoticEvil races of orcs, goblins and trolls are just as apt to fight each other as they are to attack the humans and other goodly races, until a BigBad manages to terrify them enough into cooperating under his leadership. The evil races' fear of and/or devotion to the BigBad is all that keeps them cooperating. If the BigBad is slain, the evil races will just as willingly turn on each other and the army will disintegrate. Needless to say, [=PCs=] are typically the ones who are tasked with destroying the BigBad before his armies can attack the outmatched forces of good.
** One of the most notable examples in ''TabletopGame/DungeonsAndDragons'' takes place in the War of the Lance in the ''Literature/{{Dragonlance}}'' setting. Takhisis, the Queen of Darkness and ruler of the evil gods, keeps her five Dragonarmies united through ruthless discipline and their fear of her. When she is banished back to the Abyss by the [=PCs=], the Dragonarmies turn on each other and begin fighting for power. The canon post-War setting includes five territories that are each held by a mutually hostile Dragonarmy, and are just as apt to fight each other as to attack the forces of good.
** This trope actually comes up mechanically in Dungeons and Dragons rather than just from a story point of view. There are several types of monsters who are able to create "spawn" (usually these are undead like vampires and wraiths) and for some of those monsters, those spawn are created completely subservient to their creator. It is possible to build an army of monsters like this, however killing the one who created the spawn in the first place will break the bond of servitude and cause them to act freely. This could be catastrophic for anyone that was using such a monster to create a personal army or just a way to dissipate an army with a single blow.
*** Though with the potential to turn into a NiceJobBreakingItHero moment as for some of these monsters their creator's control also serves as an effective PowerLimiter and/or RestrainingBolt -- kill the "master", and suddenly all its former created "slaves" may be finally free to achieve their true horrific potential...
** On the other hand, it's consciously averted in the adventure ''Red Hand of Doom'', where killing [[TheDragon Hravek Kharn]], who's commanding the Red Hand, doesn't cause a total breakdown. It does cause the army to retreat, but only for a few hours, at which point the result depends on how well the party performed in their overall attempts to hamper and harry the army. If the [=PCs=] have been doing a good job (disrupting their alliances, making good tactical choices, killing the dragons and giants who showed up for the battle), then Kharn's death turns out to be just the latest and greatest in a long line of horrible setbacks for the army, and it disintegrates. But if the [=PCs=] haven't been doing too well, then the army simply regroups, falls under the next-highest person in the chain of command (typically a surviving member of the QuirkyMinibossSquad, or an EliteMook if the former are all dead), and resumes the attack. It's justified, too, as the army is mostly hobgoblins, who have "organized militaristic fighting" as their [[PlanetOfHats hat.]]
* ''TabletopGame/IronKingdoms'': for both Warmachine and Hordes, the Warcaster/Warlock is the motive force keeping the walking tanks/giant monsters going, so killing one shuts down/frees their personal troops, and killing all of them (if there's more than one) is the most common automatic win condition.
* ''TabletopGame/{{Warhammer 40000}}'' loves this trope.
** The Tyranids in ''TabletopGame/{{Warhammer 40000}}'' have certain breeds called "Synapse Creatures" that connect lower-tier organisms into the HiveMind. Killing a local Synapse Creature causes the portion of the Hive under its sway to become disoriented until another one can move in to take its place.
*** Even more so with Norn Queens. Apparently, poisoning one can make entire tendril with multiple Hive Ships defenseless, at least for a while.
** Similarly the Tau ideology of the Greater Good places a tremendous amount respect and symbolic value on the members of the Ethereal caste, their ruling caste and spiritual leaders. The death of a hunter cadre's overseeing Ethereal will cause the entire cadre to [[HeroicBSOD fall back into retreat regardless of how well they were doing before]]. Ingame terms, if the Ethereal is killed, all Tau units have to pass a morale check or flee. {{Subverted}} in that while Tau initially fight with limited effectiveness, they eventually recover, and their fear and doubt will be replaced with a [[TranquilFury cold anger]] over [[MoralEventHorizon what you just did]]. Cue UnstoppableRage... [[BeamSpam with plasma guns]].
*** However as of 6th this has been removed, now it just gives the other guy an additional kill point. This was [[ObviousRulePatch likely due]] to the surprisingly common strategy of shooting your own Ethereal.
** Though not as such in the rules, this is a common way of defeating Ork Waaghs in related material - a Waagh is the result of a powerful Ork Warboss gathering together a number of warbands and going to war; killing the Warboss means that, without his charisma and domineering personality lashing them together, the assembled Orks will return to their normal habits of shooting at each other as well as the non-Orks. Best demonstrated in the ''Literature/CaiaphasCain'' novel ''Death or Glory''; when Cain kills the Warboss, one of the Orks watching the fight tries to order the rest to attack, only for another to say something along the lines of "'oo says ''you're'' da new boss?!?" and attack one another.
** When the Necrons got their first codex, they were an odd twist on this trope with the "Phase Out" rule. Instead of the usual Keystone Army trait of having big blocks of mooks that fell apart when the leader was killed, the Necrons inverted it by having some incredibly powerful leaders and vehicles that all immediately disappeared if enough of the foot soldiers were taken out (if 75% of the army was neutralized, the army "Phased Out", teleporting off the field and [[NonStandardGameOver granting your opponent an automatic win]]). This represented the Necrons deciding that they didn't have the strength or strategy to beat the enemy, and pulling out the entire force to regroup and repair.
** In Alpha Legion Chaos Space Marines specifically mitigate this trope by having no centralized leadership. In the tabletop, this translate to the opponent being forced to kill every character in the army before they can earn a victory point for assassinating the leaders.
* In early versions of ''TabletopGame/{{Warhammer}} Fantasy'', if the general of an Undead army (normally a Necromancer, Vampire or [[{{Mummy}} Tomb King]]) was killed, the army would quite literally disintegrate. This was toned down in later editions as leader units were {{nerf}}ed and killing them became a less daunting prospect, but it's still bad news.
** Dogs of War (essentially a lot of mercenary companies scraped together into an army) don't much care about their general... but if the Paymaster is killed and his treasure chest captured, [[OnlyInItForTheMoney they're likely to run for it.]]
** Inverted by Thorgrim Grudgebearer, who has the ability to grant his entire army Hatred (re-roll misses in the first turn of melee) when he dies.
** While only mentioned in the fluff, it is generally considered common Warhammer knowledge that killing a major Warboss will inevitably cause any WAAAGH to eventually collapse in on itself, as weaker Warbosses and Orcs start to [[EvilPowerVacuum turn on each other to claim the title]]. However, this has no representation in the rules -- no petty infighting is going to make them stop in the middle of a fight they're already engaged in.
** The spin-off game ''Warmaster'' has "kill the enemy's general" as one of the generic win conditions for all armies.

[[folder:Video Games]]
* Killing the opponent's king unit in [[ExactlyWhatItSaysOnTheTin Regicide mode]] in ''VideoGame/AgeOfEmpiresII'' gives you instant victory, regardless of how many other units and resources the other player still has. Of course, losing your king will do the same to you. In several campaign scenarios the objective is killing one particular enemy commander or destroying one enemy building too.
* In the single-player mode of the early ''VideoGame/{{Battlefield}}'' series games, your AI teammates are so [[RedShirt incompetent]] that they will constantly lose ground if you're not being Franchise/{{Rambo}} on the front lines next to them.
** Subverted at the end of ''Bad Company 2''. [[spoiler: Destroying the scalar weapon and killing Kirilenko makes Bad Company think that the Russians will no longer invade the US. Cue a bunch of American tanks rolling up beside them to tell them that the Russians have just started to invade through Alaska.]]
* All the units of the [[StarfishAliens Scrin]] harvest escort fleet in ''VideoGame/CommandAndConquer 3: Tiberium Wars'' are powered by [[GreenRocks Tiberium]] radiation emanating from a "Relay Node" established at the original Tiberium meteor's crash site, in Italy. While the Node has an operational range that goes as far out as the Moon, its destruction stops every Scrin unit ''on Earth'' dead in its tracks, and some even break apart. The Scrin are aware of its importance: it's ''ludicrously'' well-defended with everything from [[TimeStandsStill stasis shields]], [[ShockAndAwe Storm Columns]] and a [[CoolStarship space fleet]] to [[ImmuneToBullets phase fields]] that [[CrazyPrepared render it invulnerable]] temporarily. Additionally, their original invasion plan called for multiple redundant nodes, but they got [[ObstructiveBureaucrat sidetracked]].
* In single player ''VideoGame/{{Diablo}}'', all surviving monsters die when Diablo is killed.
* In ''VideoGame/DivinityDragonCommander'', capturing the enemy's capital building and holding it for a turn results in you taking over '''all''' of their territory and surviving units.
* In ''VideoGame/DragonAgeOrigins'', killing the [[BigBad Archdemon]] immediately ends the Blight. Justified since the Archdemon's will is what unites the AlwaysChaoticEvil Darkspawn hordes into an organized military force. The expansion ''[[VideoGame/DragonAgeOriginsAwakening Awakening]]'' subverts this -- one of your tasks as the newly appointed Warden Commander in Amaranthine is to investigate why and how Darkspawn are still making fairly organized attacks on the surface (though not on the same scale as a full blown Blight).
** This particular Keystone is also much harder to destroy than most examples. Not only is the Archdemon itself [[ThatOneBoss incredibly powerful]], it can even [[spoiler: [[BodySurf transfer its soul to the nearest darkspawn and thus be reborn]].]] So unless [[spoiler: a Grey Warden sacrifices himself/herself by taking in the Archdemon's soul (an act that destroys both of their souls) or partakes in Morrigan's Ritual which transfers the Archdemon's soul into Morrigan's developing child]], the only way to end a Blight would be to ''kill every darkspawn in existence''. Which is impossible considering they outnumber just about everybody [[spoiler: and the Broodmothers can generate more at a ridiculous pace]].
*** This is why the first Blight lasted something like ''two hundred years''.
** A smaller example occurs in ''Awakening'', where a darkspawn uses a control rod to make a bunch of golems attack you. Killing the darkspawn deactivates all the golems and allows you to loot his control rod, allowing you to [[HoistByHisOwnPetard use another golem against some darkspawn in the next room.]]
* In every ''VideoGame/DynastyWarriors'' game except for Empires (which has different battlefield mechanics), defeating a general instantly causes his troops' morale to drop permanently to zero and any officers under his command to flee. So if you can get to the generals and put them down (without getting killed, of course), you can quickly swing the battle with a minimum of fighting. There are a number of tasks (particularly in 3) that are nearly impossible to accomplish any other way.
* ''Franchise/TheElderScrolls''
** In ''[[VideoGame/TheElderScrollsIVOblivion Oblivion]]'''s ''Shivering Isles'' expansion, the Forces of Order are the [[OurDemonsAreDifferent lesser Daedra]] servants of the expansion's BigBad, Jyggalag, the [[OurGodsAreDifferent Daedric Prince]] of [[ControlFreak Order]], and are connected to Jyggalag's Obelisks of Order. The Priests of Order can activate the Obelisks and will resurrect if they are killed as long as the Obelisk remains active. The Knights of Order spawn from the Obelisks while active. The only way to deactivate an Obelisk is to overload it (by placing the hearts of the Knights into it).
** ''[[VideoGame/TheElderScrollsVSkyrim Skyrim]]'':
*** Summoned Daedra and undead will die/vanish if the person who summoned them is killed. This can comically extend to entire packs of vampires or a dungeon full of necromancers, as they will raise their fallen comrades, who then proceeds to raise more of their comrades. However, if you allow them to do this while keeping track of the last "living" one, killing him results in the entire room dissipating into dust.
*** Not to the scale of an army, but the ''Dawnguard'' DLC gives you a quest where you must fight your way through a cave of charmed Vigilant of Stendarr. It is entirely possible to ignore their attacks and take a sprint down to the vampire controlling them. Killing said vampire prompts all of its thralls to drop dead.
* A standard clause for battles in ''VideoGame/ExitFate''. Even though you and your opponent has multiple units to fight with, as long as you knock out their primary leader, the rest will flee/surrender and you win. (You get a better rating if you take them all out, though.) However, the same goes for you; if the enemy defeats the unit that represents the main character, it's immediate game over.
* ''[[VideoGame/FirstEncounterAssaultRecon F.E.A.R.]]'''s Replica Soldiers depend on a psychic commander for their orders and become completely inert when the commander dies.
* TheFederation in ''VideoGame/FTLFasterThanLight'' is guaranteed victory once you destroy the [[FinalBoss Rebel Flagship]], even if the sector, which includes the Federation's Home Base, is completely covered in Rebel-occupied nodes.
* It's mentioned in the backstory of ''VideoGame/KnightsOfTheOldRepublic II'' that after [[spoiler:the massive amount of death and destruction at Malachor V]], Revan decided that turning his enemies into allies was a better idea - and, particularly in the construction of HK-47, this trope was his primary idea on how to accomplish that: kill or convert one influential person, watch everything they held together crumble on its own.
* In the ''VideoGame/{{Langrisser}}'' series, when a commander is killed, all of its surviving soldiers are also removed from the map. It's often to the player's benefit to take out as many of the enemy's soldiers as possible before killing the commanders to get the most experience points.
* In the near future mecha chapter of ''VideoGame/LiveALive'', Akira will fight the Crusader, a skull-themed biker gang, several times during the adventure. In battle a Crusader will appear flanked by several underlings, ranging from RC cars to over-sized toy robots. Defeating the crusader will destroy all the enemies as well.
* ''Franchise/MassEffect'' - The Rachni have {{Hive Queen}}s, who reside on toxic planets. The employment of Krogan (a sentient species that evolved on a DeathWorld, so can survive on Rachni Homeworlds and attack the Hive Queens) was the turning point of the war.
* ''VideoGame/MetalGearSolid2SonsOfLiberty'' subverts this: [[spoiler:Arsenal Gear]] is designed so that it wouldn't be a keystone if it was ever actually used, because while it's almost invincible as long as it has backup, when it ''doesn't'' [[spoiler:it's so weak the BigBad is willing to leave it to the QuirkyMinibossSquad as a way of ''killing them off'']].
** The SOP can be seen as the keystone in ''VideoGame/MetalGearSolid4GunsOfThePatriots''. Sure, [[SuperSenses they give you more awareness and perfect response,]] [[BottledHeroicResolve and suppress PTSD,]] but if you lose it, [[HeroicBSOD expect withdrawal]]. Half of the game is consist of Liquid Ocelot try to find a way to control it and Solid Snake's attempts to hinder him.
* The [[ScaryDogmaticAliens Skedar]] from ''VideoGame/PerfectDark''. They had been at war with the [[InnocentAliens Maians]] for a couple of centuries preceding the game's story, and are only stopped for good when the destruction of their home planet and murder of their king crushes their morale.
** One of the bonus missions shows they're savvy about this to the point that they have ''three'' back-up kings ready to take control of their forces in case the one from the main game bites it.
* Quite a few {{RTS}} will have this as a condition on various campaign levels. The player's goal is to destroy a single unit or structure, and doing so nets a victory, no matter how many enemy units are left on the field.
* In ''VideoGame/SonicHeroes'', there are gold enemies that take all nearby 'bots with them when destroyed.
* Justified in a realistic way in the slaughterhouse level of ''Creator/TomClancy's VideoGame/SplinterCell''. The bad guys are mercenaries working for cash, and Sam's boss informs him that once he kills their leader/employer, the remaining bad guys will say "screw this" and all go home (since the guy who writes their checks is now dead).
** Although it should be noted that if you're in the line of sight of an enemy soldier when you kill this boss, they do continue to shoot at you, which can quickly turn your mission success screen into a mission failed screen, especially since your controls lock up at this point.
** The show ''Series/BurnNotice'' makes the same remark. Michael points out that if you take out the person handing out paychecks, mooks and mercenaries won't stick around to avenge him.
** Something similar happened in ''Webcomic/TheOrderOfTheStick'', when Roy throws Xykon into the portal, he is destroyed. The Goblins in the throne room surrender saying that no one is paying them anymore (though it's more likely that no insanely powerful lich is threatening them anymore). Unfortunately, the goblins tried to surrender to [[HeroicComedicSociopath Belkar]].
* The Zerg in ''VideoGame/{{Starcraft}}'' are defeated when their [[HiveMind Overmind]] is killed. The ExpansionPack, ''Brood War'', subverts this; without the Overmind to direct their actions, the Swarm launches into a mindless frenzy and slaughters half the Protoss population. ''Then'' lots of backstabbing intrigue about control of the Swarm happens. A similar effect occurs when a Cerebrate is killed, except the Cerebrates only control specific broods, or sections of the swarm. Both example however apply only to the story and lore, and not the actual gameplay, except for specific campaign scenarios.
** The campaigns themselves are rife with examples where the key to victory against overwhelming odds lies in destroying weak points; for example, "Shatter the Sky", one of the two alternate penultimate missions in ''VideoGame/StarcraftII'', tasks you to destroy a space station with overwhelming forces of zerg crawling on it by taking down its coolant towers.
* {{Downplayed|Trope}} with the Aparoids in ''VideoGame/StarFoxAssault''. As you would expect from a race of giant alien insects, they keep multiplying as long as their queen is still alive. Luckily, Beltino Toad creates a virus hat causes them tosuffer from apoptosis; killing the queen with it kills them all instantly. They were forcibly turned into a keystone army.
* In ''VideoGame/SupremeCommander: Forged Alliance'', destroying the Quantum Rift of the Seraphim stops their invasion dead in its tracks. Justified in that the Seraphim technology simply doesn't work very well in our dimension, and the Seraphim have been taking a ruthless pounding for the last few weeks, just lost two major allies, and were in the process of turning on their last one when the Quantum Arch was destroyed.
** In both the ''Supreme Commander'' game and its expansion, armies will deactivate if their Armored Command Unit is destroyed. In multiplayer mode, losing one's ACU is a condition to lose the game. Justified in that the ACU contains the only person on the field, and that all the other units are robots under his or her control. [=sACU=]'s are shown to sometimes be piloted by humans, but only in story missions.
* The Commander in ''VideoGame/TotalAnnihilation'' is a good example of this trope. If it dies, you lose and your whole army blows up. The same goes for the oppenent.
* Occurs twice in the ''VideoGame/TotalWar'' games. First, eliminating the general leading an army causes that army's morale and fighting capacity to decrease, making them much easier to defeat (though it's not an instant win). On the strategic map, removing all the adult male members of a faction's royal family (via Assassination, or by bribing / marrying them into your own faction) causes that faction to lose, no matter how many territory or armies it controls.
** ''Total War'' also includes an {{inversion}}. If a general has a lot of losses, their leadership bonus goes negative. Assassinating a general replaces him with a newly-promoted subordinate who starts at zero. So, killing an enemy's lousy general improves his army's chances for victory.
** Taken to an extreme by the Vampire Counts in ''VideoGame/TotalWarWarhammer''. Most armies will take the loss of their general poorly, but the undead units of the Vampire army will literally start to crumble should the Vampire Lord or Necromancer commanding the army perish in battle, as there's no more dark magic to sustain them. Going straight for the commander is the best anti-Vampire tactic given that [[FearlessUndead Vampire units never rout or flee and always fight to the bitter end]], but also given that Necromancers often hide in the back lines and that Vampire Lords are often skilled fighters in their own right, accomplishing this is easier said than done.
* ''VideoGame/ValkyriaChroniclesIII'': {{Invoked}} by The Nameless with the operation to assassinate [[BigBad Maximillian]]. [[ForegoneConclusion It doesn't work, because said attempt is thwarted by Selvaria.]]
* Subverted in the ''VideoGame/{{Warcraft}}'' Universe with the Scourge. The only thing keeping the Scourge from becoming an unstoppable army which would consume everything is the Lich King, who [[HiveMind controls]] the entire Scourge and stops them from doing so.
* The ''[[{{Series/XCOM}} X-COM]]'' series ''loves'' this trope. In the first game, the entire alien army is run by [[VideoGame/XCOMUFODefense a giant brain on Mars.]] In the second game, the leader [[VideoGame/XCOMTerrorFromTheDeep is hidden underwater]]. In the third game, you have to [[VideoGame/XCOMApocalypse seal off the gates to their dimension.]]
** The third game, ''Apocalypse'', is actually more of an inversion: In order to seal the gates off, you have to have already destroyed their entire city, and nearly every living thing in it. The gates are the last [[OrganicTechnology structure/organism]] to die.
** It's given a nod in ''VideoGame/XCOMEnemyUnknown''. After you take an alien base, your NumberTwo believes that you've broken the invasion. The Head Researcher, however, raises an eyebrow at that, mutters under her breath something about "Too easy", then walks off to begin researching the spoils. [[spoiler: She's right. Turns out the base was only an ''outpost'' of the main force. Played straight, and Justified, at the end of the game however. Taking out the [[FinalBoss Uber Ethereal]] kicks off a reaction that [[LoadBearingBoss causes the alien]] [[TheMotherShip Temple Ship]] [[LoadBearingBoss to implode]], taking the majority of their ships, supplies, and leadership with it.]]
** ''VideoGame/XCom2'' averts the trope - defeating the Elders still leaves the general population having to rise up against the remaining ADVENT forces.
* A popular mechanic in TurnBasedStrategy games such as ''Franchise/FireEmblem'', the ''VideoGame/FinalFantasyTactics'' series and the ''VideoGame/LuminousArc'' series: kill the boss of the stage causes all other enemies to flee, stand still or outright melt away, an InstantWinCondition.
* The highly unique role-playing/real-time strategy hybrid ''VideoGame/{{Sacrifice}}'' uses this as a foundational rule -- for both the player and their opponents. Each level is essentially a glorified arena for two (or more) wizards to compete in, and each wizard is a combination of a mobile base, resource gatherer and spell provider. DeathIsASlapOnTheWrist applies because each wizard has a connection to a mystical altar, which rapidly revitalizes them; death merely prevents them from summoning new troops or casting spells, but their army keeps on fighting. Only by defiling the wizard's altar and then slaying them can they be removed from the battlefield -- and when that happens, all of their troops drop dead, because they no longer have their master to sustain them. Each battle, then, is a constant struggle by all of the players to take out the rival wizards.
* Played with in the ''VideoGame/{{Homeworld}}'' series:
** In the first game, the mighty Taiidan Empire is defeated, and you can claim your ancestral homeworld of Hiigara, the moment you take down the Imperial flagship and the empire on it. {{Justified}} because the Taiidan had pissed off enough people that the Galactic Council, and the Bentusi in particular, take the chance to ''enforce'' your claim to Hiigara, while the Taiidan rebellion takes the chance to destroy the databank with the emperor's genetic code, thus preventing a clean succession (the emperor was mad and had killed off all the possible heirs, and cloning him would have been the only way to find a successor acceptable to the whole military. It's implied he himself is a clone of the previous emperor) and creating their Taiidan Republic while the Imperialist forces (at least those who haven't defected) fight each other to try and impose their respective leaders as the new emperor. Though this is ''far'' from the end of the conflict; the former Empire [[BalkaniseMe is now a fractious mix of bickering successor states]], and a lot of serious military hardware is in the hands of [[TheRemnant various "Imperial Loyalist" groups]] and FormerRegimePersonnel who've turned warlord or pirate.
** In ''[[VideoGame/HomeworldCataclysm Cataclysm]]'', it's not fully applied: taking down the Beast Mothership and then the ''Naggarok'' is a huge blow to the Beast, but all of that means the scattered remains of the Beast aren't near-unstoppable anymore, and there's a post-game clean-up;
** In ''VideoGame/Homeworld2'' you take down Makaan in the second-to-last mission. As his charisma was the only thing keeping the various Vaygr Crusades together, this breaks their military might in multiple lesser fleets... [[OhCrap Including the one equipped with almost indestructible planet killers]], [[NiceJobBreakingItHero that now has nothing stopping them from attacking Hiigara]]. Destroying those planet killers (using the mighty warship you killed Makaan over) is your last mission.
* ''VideoGame/DungeonKeeper'': Facing an enemy Keeper is like this: the moment its dungeon heart is destroyed, its forces go neutral and file out of the nearest portal ''en masse'', leaving its dungeon to be claimed. Possibly it's because [[PunchClockVillain they're not getting paid anymore]].
* Killing a summoner in ''VideoGame/NexusClash'' instantly banishes their minions back to the dust (or heaven or hell for angelic or demonic summoners).
* Not a story example, but it's possible to create team compositions in ''VideoGame/LeagueOfLegends'' that work on this principle. Common ones include "Protect the Kog'Maw" comps, where four champions on the team are picked to buff and protect the fifth one, a [[MagikarpPower long-ranged hypercarry who is almost unstoppable in the late game]]. Alternatively, teams that pick [[TheMedic Soraka]] and rely on her incredible healing power to keep their damage dealers alive can end up as this- because her base healing spell [[EmpathicHealing costs her 10% of her maximum HP with each cast]] and cannot be cast on herself, Soraka is regularly left dangerously close to death as the price of keeping her teammates healthy, so if the enemy team manage to ShootTheMedicFirst her entire team can suddenly collapse like a Jenga tower with the base removed.


* ''Webcomic/{{Erfworld}}'': Since the world is based on a turn-based strategy wargame, this is to be expected. If a Ruler is croaked, their Side falls unless they have an heir. Heirs can either be popped naturally or designated at great expense. When a Side ends, any units in the field disband (cease to exist), while any cities go "neutral," meaning they freeze in time until someone attacks them. If all the cities are captured or razed when the Ruler is croaked, then if they have an heir, that heir will become a barbarian, a nomadic unit without a true Side. Barbarians have a limited purse and no easy way of making more money, but if they capture another capital they can start a new Side.


[[folder:Western Animation]]
* The Joining from ''WesternAnimation/TheBatman'' are an army of robots. They are defeated twice by this: the first time by a self destruct code that had been built into the various parts they were made off. The second time they were defeated by a signal to their mothership ordering them to go offline.
* In the episode "Dark Heart" from ''WesternAnimation/JusticeLeagueUnlimited'', an army of [[NanoMachines self replicating robots]] is defeated when the heroes destroy the titular dark heart commanding them.
** From the same series, an alien army is defeated when the ComicBook/MartianManhunter frees their power source from the corrupted leader controlling it.
* The ''WesternAnimation/KimPossible'' [[TheMovie movie]] [[WesternAnimation/KimPossibleMovieSoTheDrama So The Drama]] has this. Dr. Drakken distributes toy robots around the world which turn out to be giant killer robots that he can activate with a command signal he broadcasts from his headquarters. When he launches the worldwide attack, Kim and Ron foil it by knocking out the main broadcasting tower, causing all the robots to revert back to their harmless toy forms.
* ''WesternAnimation/SuperRobotMonkeyTeamHyperForceGo'' featured in one episode the Vreen, a HordeOfAlienLocusts from the future. Their weakness was the present-day bug [[StableTimeLoop they evolved from]]; when it was found and destroyed, the Vreen disappeared.
* ''WesternAnimation/StarWarsRebels'' reveals that [[spoiler:while the shutdown command on the droid army released after Order 66 did take into effect, [[TheStrategist super tactical droid Kalani]] received the command but, thanks to his calculations, determined that it was a [[AntiMutiny trick by the Republic]] and choose ''[[AvertedTrope not]]'' to shut down himself or the troops under his command. Apparently, he was the only, or at least one of the only, droids who determined something was fishy about the command]].

[[folder:Real Life]]
* Conventional and asymmetric warfare work along this principal, with concepts such as decapitating leadership, disrupting communications, or destroying the enemy supply line the most popular. The ideal army has redundancy to prevent such tactics from collapsing it, but doing so is often easier said than done. Many a battle has been lost because the general was killed, a regiment failed to receive an important message, or the army ran out of equipment because a single bridge was destroyed.
* A common problem on Ancient Greek battlefields: when the general died, the whole army tended to rout. This was exploited by the Thebans during the Battle of Tegyra. Outnumbered four to one by their Spartan opponents, they went straight for the officers, whose death threw the Spartan army into terminal paralysis.
** It was also a problem for the Persians, whose overwhelming numbers would mean little if their emperor was killed or routed. Knowing this, Alexander the Great reversed certain defeat, first at Issus and then at Gaugamela, by personally charging through the Immortals and getting Darius III to run, causing the Persians to panic and lose cohesion just when their numerical superiority was overwhelming Alexander's troops. It was actually a major strategic weakness for the entire history of the empire, since their generals tended to lead from the front and stood right in the center of the line.
* Following the events of La Noche Triste, the surviving Spaniards and their Tlaxcaltec allies fled north while being pursued by a far larger Aztec army that cornered them in the plains of Otumba with no possibility of escape. Seeing his enemy weak and outnumbered, the Aztec general Matlatzincatzin followed the Mesoamerican custom, spread his forces and ordered them to take as many men alive as possible to sacrifice them back in Tenochtitlan. However, Cortés learned (from the Tlaxcaltecs or from La Malinche, depending of the version) that if he killed the general himself, the Aztecs, now deprived of their leader, would stop fighting and leave. There was only one chance. Cortés surprised the Aztecs by using his last 23 horses in a cavalry charge that he led himself, something that the natives had never seen before (they were under the impression, in fact, that horses were only used as pack animals), killed the general and captured his standard. As predicted, the Aztecs broke lines and returned to Tenochtitlan. Cortés then took refuge in Tlaxcala, rebuilt his forces and conquered Tenochtitlan the following year, when the city had just been ravaged by a convenient plague of smallpox (caught from the Spaniards themselves).