History Main / DoUntoOthersBeforeTheyDoUntoUs

* In ''Literature/ACanticleForLeibowitz'', this is, at least [[FutureImperfect according to]] the surviving Catholic Church) what caused [[TheEndOfTheWorldAsWeKnowIt the Flame Deluge]]. Having obtained weapons of mass destruction, every world leader decided to launch a preemptive strike on their enemies to prevent them from doing it - at the same time.

* Eren Yeager finds a way to destroy the Founding Titan, eliminating Titanization in the Eldian population. However, the intense fear and prejudice Marley has against the Eldians ([[CycleOfRevenge due to the cruelty and oppression of the Eldians against others]] in wars that ended in their eventual defeat a century before the series begins), culminating in Willy Tybur's attempt to unite the world against them, spurs on Eden and Ymir's decision to kill ''as many non-Eldian humans as possible'' (80% of the population before he is stopped) before removing the Eldians' greatest weapon.

A subtrope of IDidWhatIHadToDo, this is a stock explanation for those operating on the extremely cynical end of the SlidingScaleOfIdealismVersusCynicism. When such characters have to employ a morally dubious weapon but [[PretextForWar still care about justifying it]], this will almost always be the go-to rationalization. The argument goes that once a weapon has been invented it will inevitably proliferate and be used, and therefore the only sane response is to use it as early and often as possible. Expect to hear it as a paper-thin excuse from GeneralRipper, the WellIntentionedExtremist, or TheSocialDarwinist as they sprint gleefully towards the MoralEventHorizon with the rest of the world in tow. If one with this mindset ends up on the losing end of a conflict, there's a good chance a SelfFulfillingProphecy could play out, with the others being well willing to do to them as payback, though they may also choose to TurnTheOtherCheek, if only to invalidate the aggressor's beliefs about them. If your ''heroes'' are using this justification, you probably live in a CrapsackWorld, a world of BlackAndGrayMorality at the least or ProtagonistCenteredMorality at the worst.

A subtrope of IDidWhatIHadToDo, this is a stock explanation for those operating on the extremely cynical end of the SlidingScaleOfIdealismVersusCynicism. When such characters have to employ a morally dubious weapon but [[PretextForWar still care about justifying it]], this will almost always be the go-to rationalization. The argument goes that once a weapon has been invented it will inevitably proliferate and be used, and therefore the only sane response is to use it as early and often as possible. Expect to hear it as a paper-thin excuse from GeneralRipper, the WellIntentionedExtremist, or TheSocialDarwinist as they sprint gleefully towards the MoralEventHorizon with the rest of the world in tow. If one with this mindset ends up on the losing end of a conflict, there's a good chance a SelfFulfillingProphecy could play out, with the others being well willing to do to them as payback, though they may also choose to TurnTheOtherCheek if only to invalidate the aggressor's beliefs about them. If your ''heroes'' are using this justification, you probably live in a CrapsackWorld, a world of BlackAndGrayMorality at the least or ProtagonistCenteredMorality at the worst.

A subtrope of IDidWhatIHadToDo, this is a stock explanation for those operating on the extremely cynical end of the SlidingScaleOfIdealismVersusCynicism. When such characters have to employ a morally dubious weapon but [[PretextForWar still care about justifying it]], this will almost always be the go-to rationalization. The argument goes that once a weapon has been invented it will inevitably proliferate and be used, and therefore the only sane response is to use it as early and often as possible. Expect to hear it as a paper-thin excuse from GeneralRipper, the WellIntentionedExtremist, or TheSocialDarwinist as they sprint gleefully towards the MoralEventHorizon with the rest of the world in tow. If one with this mindset ends up on the losing end of a conflict, there's a good chance a SelfFulfillingProphecy could play out, with the others being well willing to them as payback, though they may also choose to TurnTheOtherCheek if only to invalidate the aggressor's beliefs about them. If your ''heroes'' are using this justification, you probably live in a CrapsackWorld, a world of BlackAndGrayMorality at the least or ProtagonistCenteredMorality at the worst.

A subtrope of IDidWhatIHadToDo, this is a stock explanation for those operating on the extremely cynical end of the SlidingScaleOfIdealismVersusCynicism. When such characters have to employ a morally dubious weapon but [[PretextForWar still care about justifying it]], this will almost always be the go-to rationalization. The argument goes that once a weapon has been invented it will inevitably proliferate and be used, and therefore the only sane response is to use it as early and often as possible. Expect to hear it as a paper-thin excuse from GeneralRipper, the WellIntentionedExtremist, or TheSocialDarwinist as they sprint gleefully towards the MoralEventHorizon with the rest of the world in tow. If your ''heroes'' are using this justification, you probably live in a CrapsackWorld, a world of BlackAndGrayMorality at the least or ProtagonistCenteredMorality at the worst.

* According to an issue of ''ComicBook/TheSavageDragon'', this is why [[Film/MarsAttacks Mars Attacked]] Creator/ImageComics' Earth. They fearing the power of Earth's rising Superhuman population.

* According to an issue of ''ComicBook/TheSavageDragon'', this is why [[Film/MarsAttacks Mars Attacks]] Creator/ImageComics' Earth. They fearing the power of Earth's rising Superhuman population.

* Also the reason for the First World War- Germany feared the Franco-Russian alliance would be used by the French to get revenge on Germany for the last war, and figured their growing power meant that Germany had to act first. [[/folder]]

* This is the tenor of "Dark Forest theory" in ''Literature/TheThreeBodyProblem'': with a finite amount of universe and trust between interstellar players being expensive to develop and unreliable anyways, any species is a threat, and that means any species exposing its existence is a target.

* This is the tenor of "Dark Forest theory" in ''Literature/TheThreeBodyProblem'': with a finite amount of universe and little chance to develop trust, any species is a threat, and that means any species exposing its existence is a target.

* This trope is the very basis of ''Literature/EndersGame'' by Creator/OrsonScottCard. Instead of preparing for another alien invasion, mankind chooses to attack first this time.

* In episode 7 of ''{{Series/Survivor}}'': Blood vs. Water, [[spoiler: Tina reveals to Monica that Kat wants Monica to be voted out, which would clearly break the Galang women's alliance. Monica has a grim realization:]]
--> [[spoiler: '''Monica''': I teach my kids "[[TheGoldenRule do unto others as you would want them to do unto you]]"... but you know what? In ''{{Series/Survivor}}'', I figured it out: it's "do unto others ''before'' they do unto you".]]

* Also the reason for the First World War- Germany feared the Franco-Russian alliance would be used for revenge by the French, and figured their growing power meant Germany had to act first. [[/folder]]

* ''Film/StarshipTroopers'': Both sides see the other as a hideous horde of insane vermin, who hate everything their very genes stand for (humans represent arrogance and infighting, bugs represent obedience and gluttony) and [[GuiltFreeExterminationWar will do anything they can to wipe the other side out]]. [[NotSoDifferent Fancy that.]]

* The third, unnamed Entian power in Creator/StanislawLem's ''Literature/ObservationOnTheSpot'' was attacked by ''both'' [[EnemyMine Lusanians and Kurdlandians]] for the fear of them getting hit by the DepopulationBomb they've got rumors of (or were developing themselves, it's somewhat unclear). Poor southerners never stood a chance, though the reader is left with the impression that they ''indeed'' planned [[NotSoDifferent to do the same]] to their northern counterparts. Interestingly, even the fact that the third power ''existed'' is suppressed in both countries.

* ''Webcomic/SaturdayMorningBreakfastCereal'' has a strip in which [[https://www.smbc-comics.com/index.php?db=comics&id=2124#comic a robot gains sentience]], and the scientist concludes that [[RobotWar it intends to kill off humanity]]. The robot is ''horrified'' at the notion, and the scientist can only answer by saying that it "just seems like the thing to do if you're an advanced intelligence." The robot quickly huddles up with other robots and concludes that they ''need'' to kill all humans.

[[folder:Western Animation]]
* ''WesternAnimation/RickAndMorty'': in "A Rickle In Time", Rick and his grand-kids are split into two timelines. He attempts to fix the issue by merging their timelines back together, but runs into a snag, and immediately assumes that this means the other Rick gave up on merging and has moved on to try and kill the other, motivating both Ricks to actively try and kill the other before they themselves are killed.

** Seeing that papa Stalin ''did'' break the alliance he had with the Reich at the first opportunity it became profitable...

[[/folder]]

* In the ''ComicBook/XMen'' comics, one of ComicBook/{{Magneto}}'s main rationales in his [[SuperSupremacist war on humanity]] is an assumption that humans will inevitably enslave/exterminate/oppress mutants unless mutants do the same to them first (or at least separate themselves from humans). It's one of the main sticking points in his philosophical differences with [[TheIdealist the more idealistic]] Professor Xavier.

* The Earth Alliance from ''Anime/MobileSuitGundamSEED'' uses this trope as justification for their deeds. Seeing [[BioAugmentation Coordinators]] as sins against nature for their partially artificial origins, the majority of them were driven from the earth to live in space colonies. Seeing this as not enough, the Earth Alliance destroys a civilian colony, with the casualties numbering in at least the hundreds of thousands. To prevent further nuking, ZAFT develops N-Jammers to [[ArtisticLicenseNuclearPhysics somehow stop nuclear reactions]] and ZAFT launches an invasion of Earth to stop the Alliance in part to keep them from developing a countermeasure.