History Main / KeystoneArmy

* The Joining from ''TheBatman'' are an army of robot. 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.

Despite the name, only occasionally is the vital component a {{Cosmic Keystone}}. A Variety of GoldenSnitch more commonly known as an InstantWinCondition. See also DingDongTheWitchIsDead. Compare TerminallyDependentSociety. See also FantasticFragility.

* In ''[[TheMummyTrilogy The Mummy Returns]]'', the unending army of Anubis turns to dust when the title Scorpion King is killed and ordered to take his army with him. The good army is just preventing the army from getting out into the world, they knew they couldn't win on their own.

* The Doomsday episode of ''DoctorWho''. A rift in space-time sucks up all the millions of Daleks.

BeePeople are likely to be a KeyStoneArmy if they have a HiveQueen, and as such trashing it is a good way to win the BugWar. Unlike in RealLife, the fanatical [[EvilOverlord overlord]] who has brainwashed his [[PunchClockVillain ignorant minions]] into sacrificing themselves on the hero's [[AttackAttackAttack outstretched spears]] can be taken out resulting in an InstantWinCondition. 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 upon his death/defeat/distraction. [[EasilyThwartedAlienInvasion Easily Thwarted Alien Invasions]] often employs such armies.

* Justified in {{Animorphs}}. When the heroes take control of the Yeerk Pool Ship (and Visser 3), it provides the Andalites with comprehensive intelligence on Yeerk military, that allows them to turn tides in the war and defeat the Yeerk Empire.

* In IndependanceDay the alien mothership powered the shields of the smaller city destroyers. It's destruction left the previously nigh invincible ships vulnerable to conventional attacks.

* In ''Left4Dead'''s offline mode, the player(s) lose if the only survivors left are computer-controlled, even though they should be capable of going on with only 3 of them left.

* This is a classic trope for fantasy RPGs like 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.

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* This is a classic trope for fantasy RPGs like 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 DungeonsAndDragons takes place in the War of the Lance in the ''{{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.

* In ''Star Wars: The Phantom Menace'', once Anakin blows up the Trade Federation's control ship, the droid army shuts down.
** This was subverted in the novelization of ''Attack of the Clones'' (but cut from the actual movie); the Clone Army blows up the droid control ship, shutting the droids down en-mass, only for them to all power up again seconds later when their new onboard backup systems boot up.
** The earliest StarWars example is of course the original, with the Death Star's [[AchillesHeel exhaust port]]. Reused in Return of the Jedi with the Death Star's main reactor.
*** The Battle of Yavin in A New Hope is arguably a subversion, given that the Empire came back and kicked the rebels off the moon shortly thereafter.

* ''MetalGearSolid 2'' subverts this: [[spoiler:Arsenal Gear]] is designed so that it wouldn't be a keystone if it was ever actually used, because it's almost invincible as long as it has backup. When it doesn't have backup, [[spoiler:it's so weak the BigBad is willing to leave it to the QuirkyMinibossSquad as a way of ''killing them off'']].

* In every Dynasty Warriors 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...what I call "killing the quarterback". There are a number of tasks (particularly in 3) that are nearly impossible to accomplish any other way.

* A noted weakness in armies led by a dictator. When the leader is removed, the army is useless. It's worth noting that many dictators, including AdolfHitler, JosefStalin, BenitoMussolini, SaddamHussein, Idi Amin, and [[VillainWithGoodPublicity Moammar]] [[SpellMyNameWithAnS Ghaddafi]], tend to be far better at terrorizing their populations than actually commanding their armies. Stalin arguably only survived WorldWarTwo because he was smart enough to eventually leave the strategy to his generals, who actually knew what the hell they were doing.

* A noted weakness in armies led by a dictator. When the leader is removed, the army is useless. It's worth noting that many dictators, including AdolfHitler, JosefStalin, BenitoMussolini, SaddamHussein, Idi Amin, and Moammar Ghaddafi, tend to be far better at terrorizing their populations than actually commanding their armies. Stalin arguably only survived WorldWarTwo because he was smart enough to eventually leave the strategy to his generals, who actually knew what the hell they were doing.

* France's 2002 World Cup Team. Oh my God France, how Keystone Football Team can you get?

* A noted weakness in armies led by a dictator. When the leader is removed, the army is useless.

* In ''[[TheMummyTrilogy The Mummy Returns]]'', the unending army of Anubis turns to dust when the title Scorpion King is killed and ordered to take his army with him. The good army is just preventing the army from getting out into the world, they knew they couldn't win on their own.
* In Mulan, the seemingly undefeatable army of Huns falls to a avalanche set off by Mulan's well-placed dragon missile.

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[[caption-width:262:[-Mission failed!-] ]]
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* TruthInTelevision in the form of Stonewall Jackson. The Confederate army was losing badly, and in fact in retreat, to the Union army during the first battle of Bullrun during the American Civil War, until someone said "Look! There's Jackson, standing like a stonewall!" The Union army was then routed.
** Of course, in this case, Jackson happened to be in command of a regiment of infantry who were ''also'' standing like a stone wall. Inspiring everyone else's regiments to do the same.
** Actually, the context of the statement has been lost to time: it could have been that General Bee was angrily yelling at Jackson because he refused to charge and decided to do it himself.
** Also, the Union army didn't fall apart entirely; they just ran away after the Confederates rallied and launched a counterattack. They came back for another go later, in other battles and in greater numbers.

** No more than killing the commander of any army will. During the US invasion of Iraq, Saddam Hussien's incompetence advanced the his defeat by weeks.
*** The idea here is that a dictator commonly won't permit any competent people in positions of high power in the military, and he's the unifying force. In a non-dictatorial army, the subordinates of the commander is typically competent.
** The above is one of TheThirtySixStratagems

* Alvin York, a conscientious objector in WWI, was sent to attack German machine gun emplacements. After capturing a German major, he managed to get more than 100 soldiers to surrender.
** Which is more of a played-with example than a straight one: they didn't surrender immediately when he captured the major, and it was only after [[OneManArmy the Major and the men witnessed the incredible carnage York was wrecking amongst their ranks]] that the Major decided it was useless to continue and so ordered the rest of the Germans under his command to surrender.

* [[ZigZaggingTrope Played with to all hell and back]] in the [[http://en.wikipedia.org/wiki/Battle_of_cunaxa Battle of Cunaxa]]. Cyrus the Younger, a member of the Persian royal family, decided to rebel against his brother Artaxerxes and raised an army, including some Greek hoplite mercenaries. During the course of the battle, Cyrus charged the enemy lines and got himself killed, causing his army to rout completely... except for the Greeks, who, blissfully unaware of their employer's death, stood firm and in turn forced Artaxerxes' army to retreat (but not before getting their camp pillaged). Then, finding themselves without an employer and in the middle of hostile territory, they decided to go home.
* Real armies tend to make efforts to subvert this as much as possible, usually via a combination of a clear chain of command, and enough [[ProperlyParanoid paranoia]] to keep all the high ranking officers from being in the same place at the same time. They also usually make efforts to defend strategic centers of gravity, with the most common defense being simply not letting the enemy figure out where they are. Of course, the enemy will try to keep this trope as straight as possible, so it does occasionally get exploited, with the likelihood typically determined by the relative levels of competence on both sides.