[[quoteright:327:[[VideoGame/{{DEFCON}} http://static.tvtropes.org/pmwiki/pub/images/DEFCON_Worst_Case_3194.png]]]]
[[caption-width-right:327:''VideoGame/{{DEFCON}}'' illustrates how devastating this theory could be in practice.]]

->''"And he yelled, 'My [[WeaponofMassDestruction Blue-Gooer]] is working just fine!\\
And I'm here to say that if Yooks can [[ThePoorMansAtomicBomb goo]] Zooks,\\
you'd better forget it. 'Cause Zooks can goo Yooks!'"''
-->-- ''Literature/TheButterBattleBook''

%% Moved additional quotes to the subpage.

MexicanStandoff meets LensmanArmsRace meets WeaponOfMassDestruction.

Mutually Assured Destruction ([[FunWithAcronyms MAD]]) was the doctrine that nuclear weapons, if deployed against another nuclear power, should be deployed en masse with the objective of completely destroying the other country's capacity to retaliate, and vice versa. In other words, if either the USA or the USSR ever used nuclear weapons against the other, it would be [[MutualDisadvantage assured that neither the USA nor the USSR would exist anymore]]. Naturally this assumes both countries have a large enough stockpile to accomplish this - and [[PeaceThroughSuperiorFirepower they]] [[FromRussiaWithNukes did]].

The goal of a MAD strategy is counter-intuitive: it is not to win a nuclear war, but actually to ''prevent'' one. The theory goes that if each side knows that there is no way it can survive a nuclear war, it will get too scared to start one. Unless one or more of the superpowers decides on TakingYouWithMe or is ruled by an OmnicidalManiac.

Related to this is the GameOfChicken, also known as the hawk-dove game or snow-drift game. It is an influential model of conflict for two players in game theory. The principle of the game is that while each player prefers not to yield to the other, the worst possible outcome occurs when both players do not yield.

Needless to say, this theory made people on all sides of the UsefulNotes/ColdWar very nervous. Indeed, before [[TheGreatPoliticsMessUp the end of the cold war]], most academics thought the acronym "MAD" was appropriate - the strategy seemed insane.[[labelnote:*]]To be fair, hindsight reveals that most politicians on both sides ''also'' thought it was insane, but didn't have any better alternative: nukes were a way of life since the 50's and the genie couldn't be put back in the bottle. This is also why the various nuclear weapon reduction treaties were so contentious and difficult: SALT and START faced the prospect of reducing nuclear stockpiles from "We can kill everything everywhere several times over" to "If we fired our missiles just right, we might win now."[[/labelnote]] It may come up in hypothetical WorldWarIII scenarios or works set in the late-era (1980s) of the UsefulNotes/ColdWar. With the fall of the Soviet Union, MAD has lost its value as the focus shifts to combating [[TheWarOnTerror terrorists]] who do not have access to a large stockpile of nuclear weapons.

One of the theories for why the UsefulNotes/ColdWar ended [[TheGreatPoliticsMessUp as peacefully as it did]] is that belief in this doctrine prevented the US and USSR from fighting any war directly against each other, for fear it would escalate to nuclear weapons and destroy both powers. Instead, it became a war of ideologies and economics, and [[WrittenByTheWinners according to the victors]], the US eventually out-converted and out-spent the Soviets, who then collapsed under the weight of their own system.[[labelnote:*]]This was not too far from the truth, but the reality was that the Soviet system was really good at lying to itself, and their economy had been in the shitter long before the Reagan era arms race. They were doomed either way, but the competition might have sped the process up a little.[[/labelnote]]

Where there is no parity between the two nuclear belligerents, TheMoscowCriterion is used. This was developed by the British, who could not build and fire the same number of rockets as the Sovs and who did not trust the Americans to launch their own missiles to back up a MAD doctrine - instead, the aim is to have the ability to slaughter as many of the enemy civilians as possible, thus attaching a prohibitively high human cost to a nuclear release by the more heavily-armed power.
----
!!Examples:

[[AC:Fan Fiction]]
* The backstory of ''FanFic/FalloutEquestria'' was that the megaspell was created and given to both sides to invoke this scenario and end the pony/zebra war. However, when the zebras believed they were doomed to lose the war anyway, they decided to go the "TakingYouWithMe" route and both sides ended up flinging them off.
** [[spoiler: The truth is a little more complicated. Equestria's Minister of Peace created the megaspell as a part of the CARE initiative (Communually Assured Reciprocal Existence) with the intention of it being used to augment shields and healing magic. She gave the technology to both sides, hoping that if neither side would kill the other, both would give up on the war. It took both sides about four seconds to weaponize it instead.]]
* Played with on an intergalactic scale in ''FanFic/SonicXDarkChaos''. Neither Maledict nor Allysion want the Eternal War to flare up again; when the Demon and Angel militaries collide, whole galaxies are exterminated and torn apart. But when the Metarex war distracts the Demons, Allysion realizes she can gain a massive advantage over her enemy by invading the Milky Way first. Her surprise attack quickly turns the ''entire Milky Way Galaxy'' into [[CrapsackWorld a hellish wasteland]] as the Demons and Angels go into open conflict.
* In {{FanFic/MANE}}, an uneasy standoff had held between Equestria and the USR for a decade because both sides had enough nuclear weapons to destroy each other utterly. The title is also a pun on this trope: M.A.N.E stands for 'Mutually Assured Nuclear Extinction.'

[[AC:Film]]
* Visually deconstructed in ''Film/WarGames'', when Joshua plays out every possible nuclear strike scenario.
* ''Film/DrStrangelove'' is based around this, because the Russians have a doomsday device raring to go if they get hit with a nuke. One [[GeneralRipper rogue general]] in the US air force sends nuclear bombers at Russia, because Ripper, like Turgidson, thinks it can be averted with a pre-emptive strike since the United States has a five-to-one missile superiority. The film notes that the reason this trope was ''not'' successfully invoked was because the Russians constructed their doomsday device ''before'' revealing its existence, thus negating any use it had as a deterrent in the meantime and instead guaranteeing their destruction if the Americans set it off out of ignorance (as General Ripper proceeded to do).

[[AC:Literature]]
* ''Literature/TheButterBattleBook'' features two cultures (the Zooks and the Yooks), seperated by a wall and, competing in an arms race to destroy the other side; however, each new Zook weapon (ranging from giant slingshots to bipedal mechs armed with chemical goo) turns back due to the Yooks developing the same weapon or a counter-weapon. Eventually, each side creates an apocalyptic bomb called the "Bitsy Big-Boy Boomeroo", and the story ends with with the generals of both sides on the wall poised to drop their bombs, waiting to see who will do it first.
* One such deterrent is devised in Creator/HarryTurtledove's ''[[{{Worldwar}} Homeward Bound]]''. Before that, this was far from the case, as the [[LizardFolk Race]] has better anti-missile technology than the major human powers and could be reasonably expected to intercept a large number of human nukes. Additionally, since the Race's larger Empire was unreachable, the destruction of their colonists on Earth would not cripple the Empire but would doom humanity. Throughout the ''Colonization'' books, Fleetlord Atvar is musing launching an all-out nuclear strike against all [[HumansByAnyOtherName Tosevite]] territories in order to prevent them from spreading out into the galaxy, knowing that this would likely result in the planet becoming uninhabitable. One of the purposes of the ''Admiral Peary'' is to place a nuclear launch platform in orbit of Home, the Race's homeworld in Tau Ceti, a clear case of GunboatDiplomacy: either the Race deals with humans on equal turms, or both Earth and large areas of Home will be destroyed. When the first ever FTL-capablestarship, the ''Commodore Perry'', arrives to show that humans have the ultimate first-strike capability, the Race manages to device a MAD-like counter. Should humans launch a FTL strike against the three Race worlds, the Race will launch their STL starships on a collision course with Earth. An impact of even one ship traveling at 50% of the speed of light is likely to cause an extinction-level event.
* The titular [[OneManArmy One Man Armies]] of ''Literature/MistbornTheOriginalTrilogy'' produce a similar effect: If one Great House sends its Mistborn to assassinate members of another House, the second House will send ''its'' Mistborn right back.
* The final campaigns of the Final War in the ''Literature/{{Bolo}}'' series amounted to this. The Melconians and the Concordat decided to Exterminatus every planet held by the other side at about the same time. Both sides succeeded. In the end, all that was left were scattered remnants of the surviving warfleets desperately searching for a planet that's still capable of supporting life so they can start over. As the scattered remnants of the Concordat were slightly larger, humanity technically won.
* The Salgari novel ''Le Meraviglie del Duemila'' is set on an Earth where ''every country'' has access to what basically amounted to nukes (it was written in 1907, so Salgari couldn't know about the concept), and, as it's a chemical explosive, ''every single country could potentially destroy the world'', or at least wipe off the map their enemy. Quite sensibly, all countries went to the diplomatic table and resolved peacefully territorial and diplomatic disputes and other treaties to make sure nobody would go to war. And given everyone knows there is the will to use it (as it's actually used, when one of the offshore jails for the criminally violent madmen is taken over by the inmates), it works.

[[AC: Live Action TV]]
* In ''Series/DoctorWho'' it initially looked like the Time War was a case, with both the Daleks and the Time Lords wiping each other out and the only survivors being the Doctor and the Daleks that keep popping up when they're supposed to be extinct. Then the Master turned out to be alive, and then the Time Lord Council came out of hiding, then it looked like the Doctor had pushed the button that almost wiped out both races, then it turned out the Doctor merely thought he had and actually hid Gallifrey in some kind of pocket dimension...
* "Series/Community"
** One episode had Professor Duncan abuse Chang by using his restraining order to torment the guy. By the end of the episode, it is shown that Chang has gotten his own restraining order on Duncan, who then states the name of the trope.
* ''Series/StarTrekTheOriginalSeries''
** One episode had two planets who tried to avoid MAD by simulating a nuclear war and having the people who died in the simulation shuffle into suicide booths, but leaving the infrastructure and environment intact. Which managed to keep the conflict going for over a century. Then the simulation had the Enterprise destroyed by a stray missile and Kirk quite [[OrbitalBombardment vehemently]] refused to abide by their stupid rules. The leaders were certain that they would nuke each other to oblivion now that the rules were broken, but the Enterprise left before the conflict could be resolved fully.
** The Doomsday Machine was speculated to have been intended as the ultimate deterrent, "a weapon built primarily as a bluff. It's never meant to be used. So strong, it could destroy both sides in a war." But then someone actually used it. However, many ExpandedUniverse materials suggest that it was actually built as a weapon against the Borg.
* In ''Series/{{Farscape}}: The Peacekeeper Wars'' John Crichton threatens to destroy the universe with the [[https://www.youtube.com/watch?v=RSqpmUQINE8 Wormhole Weapon]] both sides of the Peacekeeper/Scarran war have been chasing him for if they do not stop fighting this instant.
-->'''John''': "Wormhole weapons do not make [[PeaceThroughSuperiorFirepower peace]]. Wormhole weapons...don't even make ''war''. They make total destruction. Annihilation. Armageddon."

[[AC:Music]]
* The Music/TomLehrer song "We Will All Go Together When We Go" is a bleak look at the enormous scale of devastation a nuclear war would bring [[LyricalDissonance set to a jaunty tune.]]
--> Oh we will all char together when we char.
--> And let there be no moaning of the bar.
--> Just sing out a ''te deum'' when you see that I.C.B.M.
--> And the party will be "come as you are!"

[[AC:Newspaper Comics]]
* Illustrated in [[http://www.gocomics.com/calvinandhobbes/1986/03/23 this]] ''ComicStrip/CalvinAndHobbes'' comic.

[[AC:Pinball]]
* Invoked with the "Ruiner" table in ''VideoGame/RuinerPinball,'' as avoiding nuclear war is not an option.

[[AC:TabletopGames]]
* ''TabletopGame/TwilightStruggle'', being a game about the UsefulNotes/ColdWar, uses the threat of this as a NonstandardGameOver. If the DEFCON scale reaches 1, then the player responsible for playing the card that started the sequence loses immediately.
* The use of [[EarthShatteringKaboom Exterminatus]] in ''TabletopGame/{{Warhammer 40000}}''. Whatever threat was on the planet is probably dead, but now the Imperium is down a planet in a time where resources are scarce enough as it is.

[[AC:Video Games]]
* VideoGame/{{DEFCON}} is essentially a Mutually-Assured Destruction Simulator, directly inspired by the ''War Games'' example above.
* MAD: Global Thermonuclear Warfare, a little-known game by the ''Creator/SmallRockets'' (a now-defunct department of ''Creator/CriterionGames'') that predates the above-mentioned VideoGame/{{DEFCON}} is ''ExactlyWhatItSaysOnTheTin''.
* ''MetalGearSolidPeaceWalker'' discusses this and whether it works or not. [[BigBad Coldman]] intends to use the titular Peace Walker to prove that nuclear deterrence works (specifically that no man wants to go down in history as the great annihilator) by launching a nuclear strike.
* The backstory of VideoGame/{{Wasteland}} has nuclear exchanges devastating the planet because of this trope.
* [[VideoGame/{{Wasteland2}} Wasteland 2]] expands upon a group introduced in the previous game, the Servants of the Mushroom Cloud, by explaining that they believe in M.A.D. as a ''religious'' doctrine. They serve as the law enforcement of the "Canyon of Titan", holding the peace by threatening to detonate a live Titan II warhead if any raider groups attempt to take over. On a smaller scale, their "MAD Monks" offer protection to travelers through the canyon by threatening to detonate a dirty bomb (with a sizable radius) if confronted with aggressive raiders. [[spoiler: A possible option in the game is disarming the monks' warhead; chaos erupts in the canyon if this is done, suggesting that the doctrine was keeping some semblance of order there]].

[[AC:Western Animation]]
* In the French sci-fi series ''[[WesternAnimation/IlEtaitUneFois Once Upon a Time... Space]]'', an episode detailing Earth's history between TheEighties (when the series was made) and the thirty-first century (the setting) had the two major powers locked in cold war and a series of small-scale proxy conflicts due the fear of mutual destruction. [[TooDumbToLive Then the respective dictators decided to distract their oppressed people by starting a war, and launched the missiles at the same time]]. [[BlackHumour The scene is represented with the dictators pressing the launch button of the missiles and then blowing up at the same time]], [[CrossesTheLineTwice with the narration continuing with "In the year 2,200 Earth, or rather what remained of it..."]] to drive home the point ([[WhatDoYouMeanItsForKids it was for kids, so they wanted to make sure they got it]]).