OK, so you have a bunch of different factions who fight against each other all the time. Wouldn't it be so much better if they could all just get along? Unfortunately, that's not going to happen, as they all hate each other's guts.
However, it's said that the enemy of my enemy is my friend. Hence, it follows that if you want to unite people, you must create a common enemy for them to oppose.
This is not for every incidence of enemy factions teaming up against a common threat. (See Enemy Mine for that.) This is for cases in which a character invokes that trope, deliberately creating a common threat for the warring factions to unite against. A False Flag Operation may help do that, and it can work well when pitched to sides engaging in a Peace Conference, since they've already both proved to be reasonable. Compare Summon Bigger Fish, which usually has less altruistic intentions in mind.
When the common enemy you're creating is yourself, it's a type of Zero-Approval Gambit.
- In Code Geass, Lelouch makes himself this threat, and then goes a step further by arranging his own assassination, thus creating world peace. Interestingly enough, his plan runs headlong into his sister Nunnaly's plan to do basically the same thing, albeit with the Damocles rather than herself. It's In the Blood, it seems.
- The centuries-spanning Gambit Roulette of Aeolia Schenberg from Mobile Suit Gundam 00 involved uniting the various factions of the world against Celestial Being.
- The Gundam Wing manga Battlefield of Pacifists uses a similar idea. An Anti-Villain former OZ soldier wants to inspire deep space exploration by taking a lost Mobile Doll factory and placing it at Mars, suggesting that a force that powerful would force humanity to put aside their differences and unite to deal with the common threat. He gets killed by a Double Agent, but his actions inspire Wu Fei to become the threat that makes humanity grow, foreshadowing his actions in Endless Waltz.
- This is also subtly implied to be the point of Milliardo's White Fang plot in the series.
- Lord Bloodman of After War Gundam X unites the divided New Federation under his banner by using the resurgent Colonies as a common enemy.
- The entire Second Valentine War in Mobile Suit Gundam SEED Destiny turned out to be this trope, instigated by the true Big Bad chairman Gilbert Durandal. He used Lord Djibril and the rest of Blue Cosmos as his Genghis, and they played right into his hands.
- In Naruto, Sasuke wants to make himself the focus of all of the shinobi world's hatred so that they will continue to operate together instead of against each other.
- In the finale of Rosario + Vampire, Kiria Hoshi thinks that was Alucard's true plan. Alucard became a villain to unite the humans with the yokai to fight against him, so they can finally bond with each other, which was also his original goal when he was Dracula.
- The Record of a Fallen Vampire: The former vampire king accidentally screwed up everything, so he painted a target on his back by (SUPPOSEDLY) attempting to unleash an Eldritch Abomination sealed in multiple points. This cross-continental journey of dhampirs escalating their attacks (with their highest ranked officer getting stronger with each death) caused the nomadic half-vampire faction to group together, gain secret control of the entire world, and eventually take command of the moon's first terraformed city.
- Attack on Titan: Discussed within the series, in a conversation between Dot Pixis and Eren. Pixis tells him about an old story from the time before the Walls, and the idea that if people had some greater threat, the wars that plagued humanity would cease. He then jokes that this doesn't seem to be true, as humanity continues to fight with each other in a barely-maintained order. Eren dismisses this story as nonsense.
- Much, much later, Marley's leader Willy Tybur makes Eren and the other Paradis Island residents this so that Marley can gain support in their campaign to destroy the island.
- In Watchmen, the Big Bad plans to force America and Russia to put aside their differences and work together by making it seem as if a massive Alien Invasion is imminent. Whether or not it works in the long run is left up to the reader.
- Cable once resurrects Apocalypse as a common threat to unite the fractious mutants.
- Gambit once helps him for the same reason. They're both going to feel like idiots (just before dying horribly) if Pocky ever wins.
- Cable turns himself into one of these in Cable & Deadpool. He styles himself as a messiah figure while running his powers at max, knowing the world will revolt against him but hoping that a brief taste of peace would "make them hungry for more." It works out exactly as planned until Reed Richards calls in the friggin' Silver Surfer to take him down.
- In What If? v.2 #85, "What If Magneto Ruled All Mutants?", Magneto does this to unite the factions of Acolytes battling on Asteroid M.
- Camelot 3000 has an interesting version. The newly resurrected knights are not dealing well with each other, so Kai, who was always the least liked of the knights, chooses to remain in the role by acting like an asshole towards the other knights. Thus, he gives the other knights someone common to look down upon and get along with each other.
- In a Smurf Versus Smurf, the Smurfs end up in a civil war over the position of the word "smurf" in a sentence. Papa Smurf swaps bodies with Gargamel in order to give them an enemy against which to unite. It works... except the Smurfs refuse to believe he's actually Papa Smurf, and Gargamel manages to switch bodies back while in the middle of the Smurf village.
- In one Future Shock, a Sioux shaman gives a magic pipe to General Custer in exchange for his own survival. Custer uses the pipe to win the Battle of Little Bighorn, which inspires all the Native Americans to unite against the white man. The last panel shows that the Natives eventually expelled all Europeans and established a confederation, with its central administration at a pan-tribal lodge called the Red House.
- In The (Questionable) Burdens of Leadership of a Troll Emperor, Naruto eliminates the misandry and misogyny among his budding empire by taking the biggest sources of it and putting them through bootcamp. His reasons that even if they don't realize the other gender is just as capable as themselves, they'll at least be united in their hatred of the Drill Sergeant Nasty.
- In Canadian Bacon, the government of the U.S.A. tries to curb economic recession and civilian discontent by renewing the Cold War. When it turns out that Russia is not interested in playing along, the United States government and the media embark on a campaign to unite Americans in a hatred of Canada, of all countries. Turns out to be a bad idea.
- In Miracle this is implied to be the reason Coach Brooks is so hard on his players - if they're united against him, they "won't have time to fight each other."
- In Watchmen: This is the ultimate plan of Ozymandias to prevent nuclear war. He frames Dr. Manhattan for the destruction of New York City, uniting the world against a fictional super-human threat.
- Bolivar Trask from X-Men: Days of Future Past believes uniting the world against mutants will create a brighter, more peaceful future.
- The Trope Namer is Genghis Khan as presented in the Conqueror books, who pulls off an epic, two-way gambit. He starts off by spending the winter raiding Tartar camps so that when spring comes, all the Tartar clans unite to crush this annoyance. He then uses the threat of the united Tartars to unite the Mongols into a single nation, with himself as khan.
- In The Man Who Used the Universe, by Alan Dean Foster, what turns out to be this gambit on a galactic scale is one of the final stages of the hero's ultimate plan.
- Romance of the Three Kingdoms: Yuan Shao wanted Han Fu's territory because it was a source of food for his army. First, he sent a letter to another warlord, Gongsun Zan, proposing that they both attack Han Fu and split his territory. Once Gongsun was on board, Yuan sent a letter to Han Fu, warning him that Gongsun Zan was coming to attack him and that he should accept Yuan as a protector. Han accepts this, at which point Yuan uses his new position to strip him of all real power. When Han realizes he's been had, he flees to Cao Cao's service.
- God-Emperor of Dune: One major theme among the many ploys of Emperor Leto II Atreides. Foreseeing great troubles for humanity, he took it upon himself to unite and prepare them... by becoming the single worst oppressor and tyrant in the galaxy. When, after several thousand years, he thinks it worked, he gladly allows one of the billions of plans to assassinate him to succeed. In a manner he chooses.
- Jacen Solo does this in the Legacy of the Force novels. The catch? He's the threat, which makes this a Thanatos Gambit to boot.
- Illuminatus!: Among the (many, many) conspiracies is that the government(s) use this to keep the populace distracted from their own sinister agendas. A character is told to watch China after the USSR falls.
- Angels & Demons: The Illuminati are used as the enemy of the Catholic Church.
- Magnificent Bastard Havelock Vetinari manages to pull off an interesting variant; he knows the heads of the various guilds of Ankh-Morpork want nothing more than to see him "dancing the hemp fandango", but the only thing keeping him alive is one common enemy — an Ankh-Morpork without Vetinari. You don't have to be the BEST patrician to succeed, just slightly better than the alternative.
- Prince Cadram tries the straight version in Jingo, but makes the mistake of picking Ankh-Morpork (and therefore the aforementioned Vetinari) as the common enemy of Klatch.
- Ursula K. Le Guin's The Lathe of Heaven uses the threat of aliens to unite the nations of Earth.
- Nineteen Eighty-Four: Global power blocs Eastasia, Eurasia, and Oceania are locked in constant war. The alliances between the three change so that one state can never become too powerful and dominate the others. This is an understanding between the three powers that's been ongoing for decades. The real objective is to provide a focus for their own citizens' hate and Patriotic Fervor — to unify them, and control them. Thanks to doublethink, most people, apparently including the ones in charge, believe they were always at war with whomever they're at war with at the moment, so they remain passionate despite the alliances changing all the time. The government of Oceania also uses the threat of a radical revolutionary called Goldstein (who may or may not exist) to justify its policing of thoughtcrime within its borders.
- In Ben Counter's Warhammer 40,000 Grey Knights novel The Hammer of Daemons, Alaric sets up a False Flag Operation to convince people that their overlord had set up the Gladiator Revolt as part of this and unite them for the crusade. Alaric's operation works.
- The Codex Alera series ends this way, with the First Lord admitting that the last Vord Queen is useful as a distant but major threat that motivates all of the four protagonist races to get along.
- Played with in the Belisarius Series. Khusrau the Persian Emperor organizes a Pan-Persian crusade to conquer the Malwa Empire and retake the lands of Persian epics. As they were already at war with Malwa anyway, it wasn't hard to do. Khusrau admits that if he had to, he would attack Rome (his ally at the time) rather than allow a civil war. But this was more convenient.
- Khusrau also cheerfully admits that the crusade doubles as a Uriah Gambit: not only does it unite the Persian people, it's a convenient way for the troublemakers most likely to cause a civil war to end up dead.
- Used both intentionally and unintentionally in The Enduring Flame Trilogy. First, Bisochim convinces all the Isvaeni that war is coming and that they must retreat to a safe location to prepare for it, while his true intention is to keep them out of the conflict entirely. Next, when the confined conditions cause tensions to build between all the tribes, he sends all the young hunters out on a wild goose chase to search for a missing tribe. Unfortunately, these hunters decide that the cities to the north of the desert have already struck first in this war and that they must destroy them all before more invaders have a chance to arrive. The ensuing conflict cements the young hunters together as one tribe.
- In H. Beam Piper's novel Space Viking, Lucas Trask distracts his divided followers from their quarrels by inventing a conspiracy by his enemy Andray Dunnan to subvert and take over the planet Marduk. It turns out that that's exactly what Dunnan is up to.
- Saki's short story "Excepting Mrs. Pentherby" has a group of people, formerly strangers, renting a shared house together, all think of their other housemates as pleasant and easy to get along with, except for one quarrelsome woman whom they all wish would leave. Turns out she was asked by the landlord to join the group specifically to give a bunch of potentially prickly characters (mostly the women, in the belief that Women Love To Argue) someone to unite against. She enjoys the role of lightning rod because she had spent most of her previous life as a paid companion who had to be submissive and conciliatory.
- In the backstory of The Belgariad, Polgara forced the warring duchies of Arendia into peace by becoming a flagrantly-abusive tyrant who utterly destroyed any noble who declined to follow her directions, so that the nobles all decided that they'd rather put aside their grudges and work together than have to deal with her. It worked for a long time, but everything collapsed again after she left.
- The Hunger Games: In order to rally the people in the Capitol on her side and end things early, Coin blows up a bunch of children Snow gathered as human shields and makes it look like Snow is responsible. It works.
- Phule in the first Phule's Company book outright tells his two feuding lieutenants he's doing this to them, as he advises them to find out what they have in common "besides the opinion that your new captain is an unreasonable son-of-a-bitch".
- In an episode of Andromeda, Dylan is being chased by members of the most powerful Nietzschean pride while transporting another Nietzchean from a rival pride to a wedding with another rival pride. However, she's actually on a mission to assassinate her intended groom. Dylan instead draws the big bad pride out into combat with members of both the other rival prides, forcing them to join together. Thus, the Sabra-Jaguar Pride is born and the Drago-Kazov Pride is no longer the biggest bully in the playground.
- In Game of Thrones:
Cersei Lannister: We still outnumber them.
- Robert discusses this with Cersei, pointing out the threat that the Dothraki Horde poses to them.
Robert Baratheon: Which is the bigger number: Five or one?
Robert: [holding up his fingers] Five. [holding up a fist] One. One army - a real army united behind one leader with one purpose. Our purpose died with the Mad King. Now we've got as many armies as there are men with gold in their purse. And everybody wants something different.
Mance: Do you know what it takes to unite 90 clans, half of whom want to massacre the other half for one insult or another? They speak seven different languages in my army. The Thenns hate the Hornfoots. The Hornfoots hate the ice-river clans. Everyone hates the cave people. So, d'you know how I got moon-worshippers and cannibals and giants to march together in the same army?
- Mance Rayder explains to Jon that he created his wildling army by uniting them against the Whitewalkers, Night's Watch, impending winter, etc.:
Mance: I told them we were all going to die if we don't get south. Because that's the truth.
- In The Outer Limits (1963) episode "The Architects of Fear", a group of scientists turns a man into a fake alien and has him "invade" the Earth in an attempt to scare the nations of the world into cooperation.
- On a more minor scale, Dr Kelso from Scrubs takes the role of common enemy in the hospital. In one episode, he notices that the staff of the hospital falling into a series of petty disputes and arguments over the Second Iraqi War, so he deliberately makes some very visible and unpopular decisions to turn everyone's anger onto himself, that decision being he's the only one to get free coffee. He does so because they are so busy arguing that they aren't doing their jobs, and the patients are suffering.
- Jeeves and Wooster: Jeeves uses this to end the quarrels between Wooster's friends. He tricks Wooster into ringing the alarm bell, thus bringing everyone outside into the pouring rain, where they find out that the door is locked from the outside and they don't have the key. When asked why Wooster rang the alarm bell, he can't give a straight answer, and Jeeves makes him go to somebody else's house to find the key. This gives everybody else the opportunity to unite in anger against him, after which Jeeves "discovers" that he had the key in his pocket all along. When Wooster finally comes back, everybody else just laughs at him for having biked a mile in the pouring rain for absolutely nothing, and forgets that they were angry at him.
- In the Xena: Warrior Princess episode "Been There, Done That", Joxer decides to invoke this during one loop. He gets stuck full of pointy things for his trouble and ends up taking Xena and Gabrielle with him.
- In the final episode of Generation Kill, Sergeant Major Sixta reveals that he's been doing this to the battalion the entire time with ridiculous enforcement of the grooming standard to give the Marines an outlet for their stress.
- Played for laughs in an episode of Sister, Sister. When the girls and one of their friends are all at each other's throats, Lisa takes it upon herself to give them a common enemy. She annoys them enough that they're all friends again within minutes.
- Cutler's plan in Being Human revolves around destroying the facade the vampires have created to hide the supernatural from mortals, then using propaganda to paint the werewolves as the greater evil and convince ordinary humans to side with the vampires.
- Employed by the teacher on Head of the Class, on the theory that he can reunite his fractious class by getting them all angry at him and immediately revealing that it was a trick.
- In the 30 Rock episode "Winter Madness", Jack and Liz discuss this trope. Liz realizes that her problem with her staff is that they all view her as their common enemy. Therefore, she invents a fictional executive named "Dale Snitterman" to blame everything on. Unfortunately, it turns out there's a real executive with that name, so it ends up with Liz's staff storming the office of someone who has never heard of them.
- Babylon 5:
- In season four's "Rumors, Bargains, and Lies", Sheridan plays a head-game on the bickering League of Non-Aligned Worlds by sending a group of White Stars to a desolate sector of space and firing on some asteroids, then denying that there was anything going on. He also get the Centauri and Narn to agree to have the White Stars patrol their common border, and likewise deny this fact. By weaponizing the Streisand Effect, he gets the League members to unify against whatever the hell he and the White Stars are worried about (i.e. nothing) and accept the Rangers and White Stars as an international peacekeeper force, which becomes a key element of the future Interstellar Alliance.
- In the Crusade episode "Visitors from Down the Street" (an homage to The X-Files), the government of an alien race with a history of paranoia and civil wars becomes aware of extrasolar life via radio transmissions, and decides to create a fake conspiracy about extraterrestrial interference in their society. They pick humanity for their scapegoat pretty much at random and suddenly there's no more civil wars. The Excalibur crew blows the conspiracy open at the end of the episode by dropping probes onto the planet to explain what's really going on, mainly because Captain Gideon doesn't like being used.
- In the Doctor Who episode "Genesis of the Daleks", this is one of the reasons the Doctor refuses to destroy the Daleks at their very beginning.
Doctor: You see, some things could be better with the Daleks. Many future worlds will become allies just because of their fear of the Daleks.
- Then played very darkly in "The Pandorica Opens/The Big Bang," when many different alien species-Daleks, Cybermen, Sontarants, Sycorax, Terilepterils, etc all team up out of fear of the being inside the Pandorica, whom they believed would end the universe, the most terrible thing in all Creation. Then it's revealed that the being inside the Pandorica...is the Doctor himself.
- In Star Trek: Discovery, this is T'Kuvma's goal. The 24 Great Houses have been bickering and fighting with one another for decades. T'Kuvma dreams of a single reunified Klingon Empire. His plan is to summon the leaders of those houses and convince them that the Federation is their true enemy, that their Catch-Phrase "We come in peace" is a bold-faced lie, since they seek to subvert the Klingon culture. He deliberately doesn't blow the USS Shenzhou out of the sky, so that Captain Georgiou calls for backup. She does, and a dozen Starfleet ships arrive. Georgiu's Number Two thinks that the only way to deal with Klingons is to fire at them without provocation, as the Vulcans have been known to do. She doesn't know that T'Kuvma doesn't care who fires first. He plans to start a war either way. Ultimately it Goes Horribly Right: He ends up firing first when Georgiou triggers his Berserk Button with the same Catch-Phrase. Most of the Great Houses join the fight, but the Battle at the Binary Stars claims over 8000 lives, including T'Kuvma's, and the more devious General Kol of the House of Kor uses this as an opportunity to seize absolute power and leaves the House of T'Kuvma for dead.
- London and Kendrick described training with Shawn Michaels as the students beating the crap out of each other while Michaels sat back and laughed...which did end up creating a bond between London, Kendrick and Bryan Danielson and apparently, Jason Sensation, who aimed to form a clique type unit between them to takeover the way Michaels had before.
- Wicked: The Wizard explains to Elphaba that this is what he was doing by making everyone believe the Animals are evil. During "No Good Deed", Elphaba comes to the conclusion that if humanity is so bend on hating something, they shall hate her. In the end, her apparent death is what creates a time of peace in Oz under the guidance of Glinda.
- Averted in Warhammer 40,000. Despite all the prerequisites, that is a number of horrible galactic threats of all colors: hordes of Ax-Crazy barbarians, Legions of Hell, omnicidal implacable robots, and all-consuming alien locusts — nothing seems to be able to divert the three more reasonable powers from each other's throats. Each power is also riven by internal conflicts.
- Played straight in the backstory of the Necrons. The Necrontyr were on the brink of civil war when one of their leaders redirected their hostilities towards the Old Ones using the Old Ones' refusal to share immortality as a pretext for war. It worked, but the end results were so awful that the civil war the Necrontyr avoided might have been preferable.
- Played somewhat straight in BattleTech. The Word of Blake, a religious Knight Templar faction, initially started the Jihad due to unfocused, inchoate rage against the Great Houses, since the Houses ended the Second Star League (it was utterly ineffective) and rendered Blake's prophecies on the matter null and void. The Blakists soon realize that they've attacked most of the rest of humanity, and eventually decide to make the most of it by becoming a foe so terrible that the Inner Sphere as a whole will have to unite against them. For the most part, it works. For a while.
- Iron Grip: Warlord nicely subverts the very reason for which you're defending the various locations. Atelia is a very disunited country and the local leaders have problems convincing the populace to rebel against the Fahrong occupation. The titular warlord of the game, Sahrab, proposes the idea of defending some of the already doomed cities with guerilla warfare for as long as possible, only to sacrifice them afterward : The constant resiliant defence will eventually piss off the Fahrong armies and force them to carpet bomb the besieged cities, blowing them to smithereens along with the local populace. Surviving Atelians will become outraged and finally eager to drive the Fahrongi out of the land. Needless to say, the Atelian rulers are utterly desperate, so they try to pull off this idea - hoping it might be Crazy Enough to Work.
- StarCraft: The Confederacy plans to secretly allow the Zerg to rampage fringe planets as an incentive to keep dissenting colonists in line. Later, Mengsk adopts the same plan and uses it to unite the various factions into a single empire, under his own thumb. Then Kerrigan enters the picture... and uses the UED to ally herself to the Protoss, only to betray them. Then she strengthens the UED in order to get Mengsk, Raynor, and Fenix to join her against them, before betraying them too. Finally, in a bit of irony, Kerrigan becomes the "common enemy" that the UED, Dominion, and Protoss unite against. However, they aren't nearly as successful.
- Knights of the Old Republic II: The Sith Lords revealed that Revan's plan was to conquer the Republic by attacking key points, while leaving the infrastructure intact and recruiting his (or her) strongest enemies. Thus, a galaxy united under Revan's rule would be more than equipped to turn to face the external threat of whatever he encountered out in the Unknown Regions. Malak, of course, royally screwed the pooch by spoiling the plan and engaging in much more random destruction.
- Star Wars: The Old Republic and associated media make Revan's plans even more labyrinthine, in terms of motivations. Initially, Revan and Malak are sent back to the Republic as a vanguard force for the exiled Sith Empire. At first, they do their job dutifully, until they decide, as Sith often do, to rule for themselves. Thus, the initial assumptions that Revan's tactics were altruistically meant to prepare the Republic against the Sith Empire are actually not quite correct. They were meant to properly prepare his own Empire against his master's. Malak tossing a Spanner in the Works ironically becomes the one thing which redeems Revan and, arguably, saves the Republic. There is a ton of Unreliable Narrator and Depending on the Author at play here as well.
- Super Robot Wars Original Generation: This is Bian Zoldark's hidden motivation (and the game that inspired the story arc, Super Robot Wars 2). He organizes the Divine Crusaders in a bid to conquer the world, figuring that either he will unite the world's powers against an alien threat — or the world's powers will unite against him, either way being better prepared for the invasion to come.
He uses a double-layered version of this trope. He's able to create the Divine Crusaders in the first place thanks to a False Flag Operation where one of his agents provoked the aliens during a secret Peace Conference, then wipes out both forces. He then broadcasts a speech making it look like the aliens attacked government forces that were planning to surrender to them. So he makes the aliens look like the bad guys so he can unite his forces into being the bad guys to unite the world against the aliens that actually are the bad guys and then the aliens at the peace conference turn out to be a different race conveniently disguised as the bad guys and oh god it's so confusing when it's compressed like this.
- Wild Arms 2: Irving Vold Valeria finances the terrorist group Odessa specifically so he would have an excuse to make ARMs an international strike force to better combat a different threat later on. It should probably be noted that he was also willing to use Odessa for this if they won.
- Final Fantasy Tactics A2 provided a very unintentional version of a Genghis Gambit. One particularly rich individual wanted to start a construction project in the Rupie Mountains and sent various hired hands like House Bowen to evict those clans who refused to step aside. One of the big attractions in the Rupie Mountains is the heated rivalry between the Bangaa Brotherhood and the Nu Mou Nobles. Guess what this individual, via House Bowen, wound up ending thanks to intervention by Clan Gully?
- Modern Warfare 2: Played terrifyingly straight. General Shepherd deliberately incites a shooting war with Russia in order to instill patriotism, incite volunteers to the military, and unify America. If this sounds a little anvilicious, it comes across that way in the game, too. The death screens even warn about the dangers of excessive patriotism.
- In Front Mission Evolved, Cornelius Werner tries this by pointing a Kill Sat at all the world capitals.
- Two of the endings in BloodStorm have this happen unintentionally. Razor unites the planet by leading a vengeance-fueled genocidal campaign against Cyberia, stopping the supply of weapons coming from that province while making the rest of the alliance stronger. Tempest, on the other hand, accidentally reveals she started the whole mess, and all eight provinces unite in hunting her down for her execution.
- Defied in Heroes of Might and Magic IV. A necromancer rejects a perfectly reasonable plan to conquer one of the newly-emerging nations of Axeoth and rule it along with his own kingdom, because he doesn't want to become the enemy that the rest of the world unites against.
- In Assassin's Creed I, Robert De Sable attempts to persuade King Richard to form a truce with the Saracens and unite against the Assassin Brotherhood, since Altair is responsible for murdering several prominent citizens on both sides of the conflict.
- Star Trek Online:
- The mission "Operation Cooperation Conspiracy" has you help a Romulan intelligence officer basically kidnap a Vaadwaur ship and send it on a remote-controlled attack to force the Benthans (Hat: Space Police) and Hazari (Hat: Private Military Contractors) to team up, thereby strengthening the new Delta Alliance. Of course then a group of non-kidnapped Vaads turn up and you have to fight for real.
- In the Victory Is Life expansion, Bajor is attacked by a swarm of Hur'q, which turn out to have been attracted there in particular by a lure planted by none other than Odo. This way he could start the attack and have a task force ready to swoop to the rescue, in hopes of securing Alliance help against the Hur'q rampaging across the Gamma Quadrant. When he's found out, his old flame Kira Nerys is pissed, to put it mildly.
- In the backstory of Skullgirls, the last Skullgirl was Queen Renoir, who wished on the Skull Heart to end the war between her kingdom and two other nations, so it turned her into a monster all three countries had to unite against. Consequently, none of them had the resources to keep order in the border region they were fighting on, leaving the already war-torn region in complete chaos. In fact, Marie, the current Skullgirl wants revenge for the acts of mafia-backed slavers in the region.
- It looks like this trope is played with in Fire Emblem Fates. The Kingdom of Nohr is suffering of both a lack of good crops (threatening to bring up quite the famine) and inner turmoil. Therefore, King Garon stages a war against the rival kingdom of Hoshido to unite the struggling forces within his lands... However, it turns out that the Genghis Gambit is just a cover to keep people from questioning the real objective. "King Garon" is actually Dead All Along and his corpse is being used by the true Big Bad to bring ruin to both kingdoms out of a misguided desire for revenge against the humans.
- In Civilization you gain a plus to diplomacy with countries who you have teamed up with to declare war on. Depending on how you can declare war and form alliances, if you have a Defensive Pact with one Civ, and make a deal with another Civ to attack your ally, they effectively become a common foe. Defensive Pacts automatically take you to war when your ally is attacked, meaning regardless of the fact that you paid your now foe to attack your enemy and promised to join them. And because you are at war, those large payments you made become null, so you are not supplying your enemies war machine. The AI is quite capable of pulling this trick on you as well.
- Mass Effect: Andromeda: A sidequest on Elaadan has Ryder take part in a ritualized form of this, courtesy of a krogan shaman trying to end a feud between two of the warriors. Under the "Rite of Union", he tasks you to lure a wild fiend into the colony's arena and force the two warriors to defeat it together, hopefully turning them into Fire-Forged Friends.
- Stellaris: The endgame crises are designed to provoke this. Most have multiple powerful fleets that can overwelm a lone large empire. If things get so bad, some of the fallen empires will awaken and rather than vassalize you, try to form a Federation with you. Though it's only fleeting alliances. All three crisis can depopulate habitable planets they take, meaning once they are defeated there is a wide swarth of open space ready to create all new territorial disputes.
- Fanatical Purifiers, Devouring Swarms, and to a lesser extent, Determined Exterminators will tend to force allies among their neighbors. Considering that making these rivals is about all the peaceful interaction you have with them, and having similar rivals actually helps other empires become friendlier to you, this opens up a lot of potential for defensive pacts and allies.
- If the Great Khan arises among the Marauders, they will use the full empires as the outside enemy and thereby unite the Marauders into a terrifying force. If you can't go toe-to-toe with them, they will happily conquer you.
- In the event of a War In Heaven, in which two Fallen Empires awaken and go to war and not caring in the slightest for collateral damage, one event features the entire galaxy coming together to form a third faction in a desperate attempt to beat the both of them down and end the conflict.
- Tyranny has this as part of its backstory, as part of why the invasion of the Tiers went so well was due to all the factions thinking they could stand up to Kyros alone, and were more than happy to let their neighboring nation fight alone, allowing Kyros to sweep through with minimal resistance.
- Bug argues that this is what the UN should be doing.
- Apparently the reason why Tavor was made immortal in Looking for Group, so he could unite the enemies of Kethenecia into one imperialistic force that would attempt to conquer the northern tribes, who Cale could rally into rebuilding the ancient city.
- General Tarquin, Elan and Nale's father, from The Order of the Stick:
- He created a complicated plan involving a coalition of Men Behind Men working to create three "rival" empires spanning a continent between them, that are actually working together to maintain the power of their respective puppetmasters.
- On a smaller scale, Tarquin uses the threat of the other conquering nations to pressure smaller states into capitulating into his empire for their own protection. What they don't know is that his companions control those other major nations and are doing the same thing to gradually absorb every independent state in the region.
- Saturday Morning Breakfast Cereal: One strip had a hero who tricked the nations of the world into uniting and depleting their nuclear arsenal. It doesn't end well.
- The Non-Adventures of Wonderella: In this strip, Wonderella gets fed up with the recent spate of superhero infighting and puts a stop to it by dressing like a supervillain and declaring that the heroes' petty squabbling has allowed her to launch her world domination plans. They immediately come to their senses and make peace with each other.
Queen Beetle: For Dana, this was a surprisingly noble act.
Wonderita She said it's the easiest way to handle superhero bro-drama.
- King of the Hill: Bill becomes the emergency marshal of the local flood shelter and turns out to be a competent and well-respected leader... by blaming Hank for everything that goes wrong and eventually locking him up. Technically, the whole flooding of South Arlen was Hank's fault, as he opened the flood gates to prevent a possible larger flood from the dam bursting (the guy who was normally in charge of this abandoned his post and managed to completely pass the buck onto Hank). But Bill had to go and muck it up by keeping everyone effectively imprisoned in the shelter by letting them believe the flood had not yet ended... when it actually had.
- Trope Namer: Genghis Khan, who went on conquests to unite the Mongols. Cracked.com described it as something akin to a massive work team-building exercise.
- For basically everyone else though, this was subverted. One of the biggest reasons the Mongols did as much damage to civilization as they did was because every time they came around and starting massacring one faction, that group would go to their normal enemies and cry, "Oh god help us, these Mongols are the most horrific thing you can possible think of! We need to join forces to stand a chance!" And without fail, nearly every time the other faction would say, "eh fuck those guys, they had it coming" on the assumption that they would never be next on the chopping block, which they almost always were. The worst instance was when the Cuman steppe peoples got devastated, took asylum in Hungary, and begged for unification to defeat the Golden Horde. The Hungarian people out of paranoia towards their former enemies stormed the castle where the Cuman king was staying and cut off his head, causing a war with the Cumans in Hungary when the Mongols were at their doorstep.
- This was Otto von Bismarck's favorite trick. To unify All the Little Germanies into, well, Germany, he made Denmark look like an aggressor, then manipulated Austria into attacking Prussia, then France into attacking everyone. When the dust settled, Prussia had doubled in size by unifying with many of its small neighbours, France was humiliated, Austria was broken, and Denmark lost a large chunk of land.
- Ronald Reagan once openly pined for an extra-terrestrial invasion before the UN General Assembly, with the idea behind it being that said invasion would be such a singular, overriding threat to all human life on Earth that it would bring mankind together for the first time as a species to repulse their collective extra-terrestrial adversary.
- Romanian ruler Mihai Viteazul did this as a necessity, as enemies were tearing the country apart in regions. With the rest of them being somewhat subjugated to foreign rulers, he united them by force and succeeded, but only for a brief time. Centuries later, Ioan Cuza would do it in a more peaceful and in-accord way, which lasted to this day.
- Hideyoshi Toyotomi's strategy in the 1590s to unite the feuding warlords of Japan was to invade Korea and China and let the warlords deal with their carnal fury. They didn't make it past Korea.
- Part of the reasoning behind Drill Sergeant Nasty. Even if none of the 40 guys in any given platoon can agree on anything else, they can all rally behind the idea that the bastard sergeant needs to die a slow, painful, and embarrassing death.
- This was the main reason for the early Crusades. The struggle of a common cause was intended by the Church to burn away the petty resentments between the Christian lords of Europe, and the land seized was to allow estates for spare sons.
- North Korea keeps its people in line by uniting them against nothing less than the entire rest of the world (though mainly South Korea and the United States). As of March 2013 they seem to be uniting everyone else against them, since even China (pretty much North Korea's only major ally) is agreeing to enforce sanctions against them now (calling them out on North Korea being an Ungrateful Bastard of a country, even comparing them to a spoiled child.)
- U.S. Secretary of State William Seward thought that a Genghis Gambit against France, which had just established a puppet dictatorship in Mexico, would unite the Union and Confederacy and avoid the Civil War. No one else bought the idea.
- Crops up once in a while during the long process for the unification of Italy:
- First it was Carlo Alberto, king of Sardinia, to successfully paint Austria as the common enemy of all Italians, leading a coalition against them in the 1848 war. It ultimately failed because the Pope and the king of Two Sicilies didn't buy it and ultimately decided to recall their troops and leaving Sardinia to fight alone (it helped they had not officially declared war, thus painting the commanders as rogues);
- Between the 1848 and 1859 wars, the Count of Cavour (prime minister to king Vittorio Emanuele II, Carlo Alberto's successor) almost succeeded in doing it and creating a confederation where Sardinia would become a Kingdom of Northern Italy and the Two Sicilies would become a Kingdom of Southern Italy, with the two countries conquering the rest of Italy and Austria as the enemy. It ultimately fell through when the king of Two Sicilies asked what about the Pope and found out the original plan, calling for three kingdoms with Central Italy and the confederation led by the Pope, had been discarded upon Papal rejection;
- After that, Cavour conspired with Napoleon III to unite Sardinia, the Italian patriots and the Second French Empire against Austria. This time they succeeded, leading to some progress on the unification;
- the transformation of Sardinia in the Kingdom of Italy came after another successful round from Cavour, this time by presenting Garibaldi's conquest of the Kingdom of Two Sicilies as the common threat to both Sardinia and most of Italy to get Britain and Austria to let him conquer the dukedoms of the North, most of the Papal States and the Two Sicilies and the king of Two Sicilies as the common threat to his own subjects so they'd allow Garibaldi to conquer them (Garibaldi was on the plan);
- Italy was allied with Prussia when Bismarck manipulated Austria into attacking them, and managed to conquer Venice;
- failed and then succeeded by accident during World War I: Italy tried to paint Austria-Hungary as invading barbarians ready to Rape, Pillage, and Burn to motivate the soldiers (who still identified more by their region of birth than as Italians) into fighting, but they didn't buy it (partly because they could see they were invading Austria-Hungary), but then, after the rout at Caporetto, they saw the civilians (who had bought the propaganda) running from the Austro-Hungarians (who were now actually invading), and rallied together as Italians. One year later, the Austro-Hungarian Empire had collapsed.
- One of the reasons Canada exists the way it is today. The regions that made up the original provinces (and PEI) were not particularly interested in joining up due to historical and cultural differences (see: Quebec) so a group of politicians (now referred to as the Fathers of Confederation) riled everyone up by hyping the danger of American Manifest Destiny (which was actually a real danger but not quite to the extent they made it appear).
- Within Quebec itself, such a tactic is often used to unify warring French factions when told that Montreal is poised to become an international force. The reason? Montreal continues to have an English character and therefore (in their eyes) threatens the existence of the French fact.