No one wants a war; War Is Hell is after all. Yet there's always someone out to start a war, leaving it to the heroes to stop hostilities from escalating. The factions can be anything from galactic empires down to street gangs. They might have originally been allies or begrudgingly upholding a tense peace. Usually there's a villain who wants to start a War for Fun and Profit and sets out to trick the factions with a manufactured Pretext for War. Sometimes a leader or member of one of the factions is a General Ripper who wants there to be war to prove a point or for patriotism. In the worst cases, the entirety of both factions is filled up with people raring to fight, and only the efforts of a Reasonable Authority Figure and the heroes is holding the peace. And sometimes, a nation supported by entirely Arms Dealer and war economy would demand more wars.
If there aren't any villains out to incite war, then it's likely a morality play about how even good people can act foolish and go to war. In such cases, the provocation itself might not even be a slight or offense, it could be a pair of Star-Crossed Lovers from each side choosing to elope (and each side assuming the other one seduced or kidnapped their lover), a natural resource about to run out (and neither side wants to share), or a misunderstanding.
Though the heroes usually succeed, stories where they fail are not unheard of. It can easily turn into a Tragedy (Impulsiveness optional but common). In these cases, one or both sides may have hawks who believe War Is Glorious and seek to start one by whatever means possible.
If the characters are trying to prevent a historical war, there can be overlap with You Can't Fight Fate and You Can't Thwart Stage One (unless it's an Alternate History). Another popular plot during the Cold War was to stop the West and USSR from starting World War III, or Avoiding the Great War in the case of WWI. World War II is different because it often runs afoul of Hitler's Time-Travel Exemption Act.
- One Piece: The entire Alabasta Arc follows this plot: The leader of Baroque Works plans to plunge the kingdom into civil war so he can steal a superweapon in the confusion.
- In Comic Book/Watchmen Ozymandias fakes an alien attack on New York to prevent a nuclear war between the USA and the USSR.
- In Sin City (as well as the film version), Dwight has to cover up the death of a Corrupt Cop to avoid a war between the police and the girls of Old Town. The event is being orchestrated by a local come lord, since the war with the cops will leave Old Town vulnerable to a takeover by his forces.
- The film version of The League of Extraordinary Gentlemen has the heroes tasked by the British Government with stopping the villain's plot to destabilize European geopolitics and starting a war. It's revealed at the end that he's doing it to boost his arms sales.
- Tomorrow Never Dies has Bond and Chinese agent Wai Lin try to stop a media mogul from manipulating the United Kingdom and China into war for better ratings and exclusive media rights in the latter.
- This is actually a recurring plot in the Bond movie franchise. The first time it appears is in You Only Live Twice, before being repeated in The Spy Who Loved Me and Tomorrow Never Dies. In the first film, the villain is trying to provoke a war between the United States and the Soviet Union, for the benefit of his employers (implied to be Red China) who hope to dominate the world once the superpowers have destroyed themselves. In the second film, the villain is an Eco-Terrorist trying to provoke a nuclear war that will destroy civilization, so that he can rebuild it to his own specifications.
- Octopussy is a twist on this. The villain wants to explode an atomic bomb in West Germany and blame U.S. carelessness with its nuclear arsenal, so that European populations will insist on unilateral disarmament, and therefore leave themselves exposed to a Soviet invasion. So, really, it's "prevent the peace... lest it lead to an actual war."
- The Living Daylights is a toned down version of this. Again, the villains are provoking the British and Soviets into a confrontation with each other; however, they're not trying to provoke a war, just trick the British into eliminating a senior KGB general before he can bring them down. Ironically, they do this by trying to convince the British that he might provoke a world war, being a homicidal maniac who's targeting Western intelligence officers for elimination in a policy that might easily escalate into nuclear war.
- The Princess Bride has Prince Humperding try to start a war with a neighboring country by staging the kidnapping and murder of his fiancé and blaming it on them. It's stopped, albeit the Dread Pirate Roberts' attempt to stop the war be purely coincidental to rescuing Princess Buttercup.
- At one point in Troy Helen says she would rather go back to her husband Menelaus, whom she didn't love, than stay in Troy and risk war and loss of life. Paris even suggested a duel with Menelaus as this was (theoretically) a personal quarrel. Both were refuted by Hector and Priam since Agamemnon, Menelaus' brother, was using Helen's cuckoldry of Menelaus as a Pretext for War. They let Paris try his duel though insisted Helen stay. Agamemnon told Menelaus to accept, because it would give him personal satisfaction and they'd attack the city regardless.
- The plot of Star Trek VI: The Undiscovered Country reveals that there is a conspiracy of old die-hards ironically composed of both Starfleet and Klingons who want to stop the peace movement between the Federation and the Klingon Empire. If the peace talks failed, odds are the resource starved Klingons would start a war with the Federation. Captain Kirk takes up the cause of thwarting the conspiracy after coming to terms with his own hatred of the Klingons, and ends up securing the accord in the end.
- Gulliver's Travels (1939). The kingdoms of Lilliput and Blefuscu are on a path to war. Gulliver must find a way to stop the war before it destroys both countries.
- In X-Men: First Class, Charles Xavier and Erik Lehnsherr must stop Sebastian Shaw, who is playing both the United States and the Soviet Union into starting World War III.
- Jack Strong has preventing World War III as his primary motivation for working with the CIA.
- The Hunt for Red October plays with this. The U.S. Navy believes that this is what they're trying to do, having been told by the Kremlin that the titular submarine is commanded by a rogue officer who intends to fire nuclear missiles at the United States. In reality, he's trying to defect to the United States, and much of the film revolves around the protagonist's efforts to convince the Navy of this. (Note that the novel averts this plot entirely. The U.S. government comes to the right conclusion almost immediately: their main dilemma is what to do about it).
- Luna Aeternal: The story revolves around Twilight and Princess Luna going to a human moonbase to sign a peace treaty, meanwhile a joint taskforce composed of genocidal racists of both species intends to cause a terrorist attack that will ruin any chances of it happening.
- In A Brother's Price preventing a second civil war is a major plot point, this is why the princesses may not marry as they choose: They cannot, under any circumstances, split the family. (Splitting the family means that the elder set of sisters have one husband and the younger ones have another - men are rare) The princesses are also shown acting as judges, which is important to avoid people taking conflicts about land rights into their own hands.
- Diplomatic Immunity by Lois McMaster Bujold has the hero who is an Imperial Auditor (big-time troubleshooter) sent to calm down a harbor brawl that had escalated into an interstellar incident, only to find that there are more sinister aspects that threaten war with a rival empire.
- Ender's Game: Ender's siblings Valentine and Peter pick up evidence of the New Warsaw Pact gearing for war, as the current peace is based solely on fear of the alien Formics, who are about to be defeated. They adopt false identities as the demagogues "Locke" and "Demosthenes" to warn citizens over the nets about the broiling situation in Russia.
- The P.O.V. Sequel Ender's Shadow has Bean, a Battle School graduate, do research of his own and see it's not just Russia who's preparing for war. He contacts Locke and Demosthenes (unaware that they're the siblings of his classmate) warning them about other nations to look out for, and also to petition to let the Battle School children come home after the war.
- In both the book and film versions of The Sum of All Fears, the villains are attempting to provoke a war between the USA and the Russians by detonating a nuclear bomb at the Super Bowl, and by instigating another attack; in the book, East Germans disguised as Russian commanders get the Russian tanks to fire at the American tanks near Berlin, in the movie, a well-bribed Russian air force general instructs his air wing to attack a US aircraft carrier. Jack Ryan and John Clark have to find out what really happened before one side starts nuking the other.
- In The Elenium, after Sparhawk destroys Azash, the heroes are at pains to prevent King Wargun from launching a genocidal war against Zemoch anyway, despite the Zemochs being entirely nonthreatening without the lash of their dark god.
- Smaller-scale than some of these examples, but early in the Malleoreon Garion gets to bully two armies into going home and not (potentially) starting a civil war.
- In the first Rivers of London book the B-Plot is that the two Anthropomorphic Personifications of the Thames, and their families, are gearing up to go toe-to-toe with each other (with the implication that it will be very unpleasant for everyone living in the Thames valley, estuary, and catchment area) and our heroes need to find a way to force a truce.
- This is why a certain Major Perry Rhodan of the US Space Force decided to cut his ties with his employers and nation and set the STARDUST down in the middle of the Gobi desert to set up his own independent operation rather than land where he was supposed to when coming back from the Moon, back when the series started — the threat of the alien technology he found there falling solely into American hands could too easily touched off a preemptive World War III otherwise. (An actual attempt at a global nuclear exchange between the three power blocs of that Earth's 1971 Cold War does take place not long after and is only foiled when the alien cruiser still on the Moon uses said technology to prevent the warheads from detonating.)
- The Thirty-Nine Steps begins with this as Richard Hannay's motivation, trying to warn the authorities of the impending assassination of the Greek Prime Minister, Karolides, while being pursued by those responsible. Given Karolides is an expy of Archduke Franz Ferdinand, you can imagine how things play out... After this, instability in Europe leading to war becomes almost inevitable, and the rest of the plot is Hannay working with the British Military to prevent the Germans obtaining vital military secrets.
- Teased but ultimately averted in military science fiction Victoria. At first, Captain Rumford opposes his leader, Governor Kraft, in the latter's crusade to start a war against the transhumanist Lady Land Azania, but eventually he comes around to Kraft's point of view and agrees that a pre-emptive war is the only proper policy.
- Throughout the first season on Mob City, Stax, an Amoral Attorney for the Mob, tries to prevent the situation in Los Angeles from escalating into a Mob War. He invokes Pragmatic Villainy to convince rival mobsters to not hurt the patrons and staff at a casino run by Mickey Cohen and later arranges a sit-down between Cohen and rival mob boss Dragna where they agree to a temporary peace. However, his efforts seem to be for naught when at the end of the season Teague kills Ben 'Bugsy' Siegel and a massive power vacuum opens up.
- Star Trek: The Next Generation and Star Trek: Deep Space Nine had a treaty with the Cardassians after a bloody conflict. However several Federation colonists were left in DMZ and at the tender mercies of their Cardassian neighbors. Soon tensions escalated into an all out war between the colonists.
- Babylon 5 was supposed to be a Space Station to prevent war after the Earth-Minbari war. As the later seasons show, it failed.
- Doctor Who:
- Several stories, especially "Frontier In Space", in which the Master is trying to start a war between the Earth and Draconian Empires so that the Daleks can attack both when they're exhausted.
- There's actually a DVD special feature on that story which draws attention in a rather Take That! way to the fact that Doctor Who had stories in which war was actually prevented, whereas certain more recent American space opera shows (*ahem*seeabove*ahem*) like to depict the heroes fighting unsuccessfully for peace for just long enough to allow a war to break out, so that they can have an exciting war arc without making the heroes look too aggressive and jingoistic.
- The first season of The 100 has several violent skirmishes between the 100 and the Grounders whose territory they've landed, motivating Finn to arrange a meeting between Clarke and the Grounders' leader to discuss a peaceful resolution. However, the peace talks collapse because both Clarke and the Grounders' leader expected the meeting to be a trap, and so they both had gunmen or archers hiding just outside the peace conference. When those soldiers spot each other, the shooting starts, and the Grounders declare an all-out war of extermination on the 100.
- The Man in the High Castle: Nazi Germany and the Japanese Empire were the victors of World War II, but have been in an uneasy truce with each other ever since. The Nazis in particular want to take the Master Race idea to the next logical step and wipe out their last potential enemy to achieve total world domination. Since the aging Adolf Hitler is one of the few opposed to this, his death may spell more disaster for the world. Throughout the series, members of both the German and Japanese governments conspire with each other to prevent a devastating nuclear war.
- Shadowrun adventure Elven Fire. Someone is trying to start a gang war in Seattle between the Ancients and other gangs. The PCs are hired by a Lone Star detective to prevent this from occurring.
- In Nomine supplement The Final Trumpet. Two Demon Princes are trying to start a war between Heaven and Hell before its appointed time. The PCs' job is to stop them from succeeding. If they fail, Armageddon will occur.
- Eberron has a suggested hook in the "Forge of War" sourcebook that the players could either travel through time or play characters at the beginning of the Last War, and thereby attempt to prevent it.
- While the initial task of the protagonist of Nival's Hammer & Sickle (a sequel to Silent Storm) is to infiltrate West Germany in order to form La Résistance and work against the Western Allies, he/she quickly discovers that a secret organization is running False Flag Operations to turn the Cold War into World War III. The same organization was the enemy in Silent Storm, selling advanced weapons to the Allies and the Axis during World War II in order to get both sides to devastate one another and take what's left.
- This appears in the Baldur's Gate series, although since the games don't force a particular moral outlook or motive for the Player Character, it's up to the player whether stopping a war is actually a goal for them or something they just do on the side while defeating their enemies.
- The plot of the first game ultimately revolves around preventing a war between the city-state of Baldur's Gate and the nation of Amn. The tensions leading towards war are being purposefully stoked by the merchant—criminal organisation Iron Throne — though, somewhat ironically, most of the leaders of the Iron Throne in Baldur's Gate start to actually smooth down relations towards the end of the plot because they think they've gone far enough in benefiting from what has already happened and want to avoid the actual war. This doesn't suit the plans of the real Big Bad, who wants the war for more sinister reasons.
- In BG II: Shadows of Amn, a side plot involves stopping the invasion plans of the drow elves against their surface elf enemies.
- In BG II: Throne of Bhaal, the war is already going on, but prophecy indicates that the player character's success will prevent it getting worse by a whole magnitude.
- This trope eventually becomes the main conflict in the Kingdom Hearts series. The Big Bad wants to restart the legendary Keyblade War, so he can take the Cosmic Keystone it was fought over and use it to reshape the universe to his liking.
- Schlock Mercenary has an unusual variant, in that the people trying to prevent a civil war in the UNS mostly function as the bad guys. Admittedly, this is because their strategy for preventing it involves remotely erasing the minds of innocents to serve as meat puppets for the mind of a ruthless killer, clawing for any advantage they can, and more than a few mass murders. Occasionally they even risk starting other wars in order to ensure it.
Admiral Emm: You raise the spectre of war as an excuse to let these so-called diplomats run free. Do you have any idea what kind of war awaits us if they reveal the secrets they carry?
General Bala-Amin: I'm going to hazard a guess and say "civil war".
Bala-Amin: You've left me wondering whether you and I would be fighting on the same side.
- We Are All Pokémon Trainers
- The main point of the Abbyfall quest in PMD-B was to prevent the Bay region of Hoenn from exploding into war once again.
- Tagg's group in PMD-B hands over the letter stating the Hoennese royal family's claim to the Pokepanese throne to the Hoennese emperor in order to head off any wars of regional supremacy by powers who would view it as a threat.
- Avatar: The Last Airbender: This is basically the reason Avatar exists. Avatars try to maintain a balance between the four Elemental Nations in the world. In the first series Aang rather tries to stop an ongoing war but in the sequel series, The Legend of Korra, the new Avatar tries first to prevent a war between benders and non-benders, then another one between the Southern and Northern Water Tribes. It is even revealed in an Origins Episode that the cycle of the Avatar begun for the sole reason that the first Avatar couldn't stop people from fighting each other after he himself had accidentally released chaos into the world.