Something similar happens in Mobile Suit Zeta Gundam, as two of the highest ranking living Titans briefly struggle for control of the organization at the end of the series after Jamitov is killed by Scirocco.
Mobile Suit Gundam Wing went a different route. Treize resignes from OZ in protest at the imminent introduction of pilotless mobile dolls. He is exiled to Luxembourg, but a group of OZ soldiers who agree with his ideals remain loyal to him, quickly leading to all-out war between OZ and the Treize faction.
Another prominent example is OZ versus the remnants of the United Earth Sphere Alliance in the early episodes. Most of the latter faction either surrendered due to the confusion and heavy losses (since OZ was supposed to be allies), and the few who held out were eventually destroyed by OZ forces.
It is implied that it is precisely this that maintains the tenuous Balance of Power in the One Piece world. Lack of unity is the only thing that keeps the Four Emperors (the four strongest pirates in the One Piece world) from becoming an even greater threat than they are already. This can also apply to a lesser extent to the other half of the Balance: The Marines and the Seven Warlords of the Sea, and even amongst the Warlords themselves, as it's stated at one point the mere idea of a group of Warlords fighting as a team was unthinkable.
The Marines are the faction with the greatest unity, following the rule of "Absolute Justice". However, it's clear that some of the officers don't give a crap about justice and just want the perks that come with their power. And then there are those Marines that don't follow "Absolute Justice" but follow their own personal brand of "Justice" (usually called "Moral Justice" but some characters develop their own, such as Aokiji's "Laxy Justice"), such as Admiral Aokiji and Captain/Commodore/Vice-Admiral Smoker.
In Slayers, the Five Retainers who lead the Mazoku can't stand one another. Chaos Dragon is openly in rebellion against the others and devotes all his energy to ruining their plans. Hellmaster has lost faith in Dark Lord Shabranigdu's ability to end the world and wants to do it himself. Dynast, on the other hand, wants to immediately resurrect Shabranigdu for another go at it. Greater Beast loathes Hellmaster for always bossing her around, but also thinks that Dynast's plan is too reckless. Deep Sea has her own plan, thank you very much, and isn't happy when other plans get in the way. As a result, the Mazoku spend more time and energy undermining each other than fighting the heroes. Most of Slayers: NEXT is an Evil Plan by Hellmaster to get rid of Chaos Dragon (and may have been a plan by Greater Beast to get rid of both of them). In the final light novel, a full-scale civil war breaks out, with the only ones who seem to have any sort of camaraderie are Greater Beast and Deep Sea (ironic, as Fanon had speculated that they hated each other up until that point.)
In the Namek arc of Dragon Ball Z, the fact that Vegeta had turned against Frieza and was (single-handedly) taking down his Mooks and Dragons one by one was probably the only reason why the Good Guys stayed unnoticed and alive for so long.
Baron Ashura and Count Brocken in Mazinger Z. So, so much. And then you have Archduke Gorgon, who did never miss one chance to show he despised and mocked all of them, and had his own agenda. And Viscount Pygman, who was the only Hell's servant argued with Gorgon and rebelled against Dr. Hell and became The Starscream.
Great General of Darkness and Marquiss Janus from Great Mazinger were at odds with each other before the death of the former.
Neither Blackie nor Gandal from UFO Robo Grendizer cried when Duke Fleed killed Barados off. Gandal himself/herself is an -amusing- example, since he/sher had split-personality and for a short while was in war with himself/herself.
The Witches 5 group in the Sailor Moon S anime. They go as far as killing two of their members to take leadership: Mimete tampers with Eudial's car and causes her to have a "fatal accident", and later Mimete dies when Tellu plugs off the Witches Electric Warp machine she's using and shuts her off forever. In fact, major Sailor Moon anime villains get rid of each other or themselves a lot - presumably so that the heroes have less blood on their hands, what with the main villains usually being more human-like than the monsters of the week. In the manga, the heroes kill them.
Played with in Fang of the Sun Dougram. Technically, the rebels are fighting against the whole of Earth Federation, but in reality they're only fighting the Earth region of Medohl (Europe) and its ally Mardo (South America). Representatives of Cohord (Russia), Mingus (North America) and Rodia (Africa), which are opposed to Medohl, gladly provide the rebels with resources, hiding places and training grounds for their fledgling army, gambling that Medohl's representatives won't risk civil war.
Deconstructed in Marvel Comics'Earth X. Mephisto has deliberately created multiple universes full of lesser Devils, precisely so they will fight and plot against one another, creating chaos that spawns disasters while also obfuscating his own plans.
The G.I. Joe comic eventually had a civil war within Cobra, pitting Serpentor against Cobra Commander (Fred VII, who had The Baroness supporting his deception). The Joes sided with Serpentor for political reasons (as well as a black box Serpentor's Star Viper had stolen from the Joes). In the end, Serpentor was killed, and Dr. Mindbender (who'd sided with his creation) quickly negotiated a settlement with Fred, leaving the Joes hanging. Destro only showed up to retrieve the Baroness.
There was another Cobra Civil War in the Devil's Due series (between Cobra's main forces and the Coil), but this series has since been "disavowed" by Hasbro.
The new IDW series, which reboots the continuity after the end of the Marvel series, is including its own Cobra Civil War.
The animated series did a riff on this idea, when a band of Joes accidentally got transported to an alternate universe where Cobra had long won the war and taken over the world. Before finding a way to return home, the intruders managed to spark a civil war between the two factions controlled by Cobra Commander and Destro. (This conflict was highlighted more than once in the "real" universe, but it never came to open blows.)
In The DCU, the mini-series Reign In Hell features a civil war for the control of Hell fought between the demon princes Neron and Lord Satanus.
The Flash series actually had a story arc called RogueWar wherein he had to stop three separate factions of villains from killing each other and a bunch of innocent bystanders. Four if you count Zoom as his own faction.
Occurs with the New York branch of The Foot after the Shredder's death in Teenage Mutant Ninja Turtles, with several factions fighting each other for control of the city. Among them are the Foot Elite, a group of Shredder loyalists who indiscriminately kill all the other groups. Later stories, such as Tristan Jones' recent issues of Tales and Volume 3, deal with the war's fallout.
This is a central theme in Star Wars: Legacy, in which the Empire has split into two factions: Roan Fel's Empire and Darth Krayt's Empire.
Dormammu and Umar, two of Doctor Strange's greatest foes, are twin siblings who rule the Dark Dimension. Whichever one is out of power at the moment is constantly scheming to take the throne back, and any alliances are loaded with ulterior motives. This is very fortunate for the rest of us, since if the two of them ever actually cooperated, they could take over the world with ease.
Whenever there are supervillain team ups in Spider Man, this trope is frequently the reason he beats them. In fact, Spidey will often goad the villains into fighting each other or trick them into accidentally hurting each other, which frequently triggers the former.
Given that most Spider-Man stories take place in New York, organized crime is often an element. Villains like the Kingpin, Silvermane, and Hammerhead have been engaged in turf wars, which sometimes involve supervillains like Doctor Octopus or the Green Goblin.
In the Uplifted series, this how the Allies view the German Civil war.
The Immortal Game has one of these in the Back Story. During Titan and Terra's original reign over Equestria thousands of years ago, she eventually got tired of sharing power with him and attempted a coup, leading forces loyal to her (including Luna) against those loyal to Titan (including Celestia). Eventually, Celestia and Luna got tired of the pointless death and destruction and engineered a Final Battle for the war, wherein they stabbed both of their weakened parents in the back and sealed them away.
The Fall of the Fire Empire: Turns out that invoking this trope is part of Azula's master plan — she sends identical messages to every high ranking officer in her military, telling them that after she dies they, and they alone, are to rule as regent until her — nonexistent — heir comes forward. She knows that this will lead to a civil war that will tear the empire apart, allowing her to effectively pull Taking You with Me on the entire planet.
In the 2010 film Predators, we learn that there is a blood feud going on between the "original" race of Predators and a new, more frightening, breed of Predator. The survivor's fight with the latter leads to an Enemy Mine truce with the former.
Further to the Star WarsExpanded Universe examples in Literature, there is Vader and Palpatine, each seeking to use Luke against the other.
This in turn continues the Sith Rule of Two, which encourages the Master and Apprentice to scheme against each other while (theoretically) keeping things from getting TOO out of hand by limiting the Sith to two members.
The Star Wars films have a particularly odd version of this trope, when you remember that both the Republic and the Separatists were under Palpatine's control, especially after Order 66, at which point the Clones were officially bad guys.
Played for laughs in Monty Pythons Life Of Brian, where there are at least five independent rival resistance groups: the Popular Front of Judea; the People's Front of Judea; the Judean People's Front; the Judean Popular People's Front; and the Campaign for a Free Galilee. Naturally they are all too busy fighting amongst themselves to get anything done.
This was referenced in the miniseries Masada where the Jewish leader, Elazar ben Ya'ir, tells the Roman commander that the secret to defeating the Jews is to leave them alone. They'd end up killing each other without a common enemy to fight against.
Part of Rogue's plan in War is to get a Triad leader Li Chang's right hand man to turn on him.
The Matrix trilogy has a whole underworld of rogue programs, who are obsolete programs that chose to go into hiding in the Matrix rather than face deletion. One such program, the Merovingian, is something like the program version of a crimelord and holds a great deal of power and influence in the Matrix. And then of course there's Agent Smith, who became an Omnicidal Maniac and attempted to destroy everything, man or Machine.
There isn't much Machines vs. rogues action seen on-screen, though there are a few glimpses here and there, most notably during the freeway chase in the second film. Morpheus and one of the Merovingian's henchmen are at one point grappling each other to a stalemate when an Agent suddenly leaps onto the hood of the car and tears the roof off; they promptly drop everything and start shooting at him. *
On that note, it's kind funny to note this is a chase scene where the original pursuers end up getting blown up halfway through, and the rest of the scene involves a party that's chasing them for entirely separate reasons.
The Dark Lords, the Big Bad of the Lone Wolf gamebooks by Joe Dever, are twice engaged in civil war after Lone Wolf kills the one in charge, giving him time to rebuild the Kai Order after they destroyed it.
In the wake of the Darklords' defeat after Book 12, the remnants of their armies fight amongst themselves to control what's left of the Darklands. Book 14 has Lone Wolf infiltrating a city fortress caught between two warring Darkland factions.
In the Star Wars: Darth Bane trilogy by Drew Karpyshyn, the main character, Darth Bane, recognizes this as both the Sith's main strength and greatest weakness. While the in-fighting culled the weak from the Sith Order, it also allowed many weaker Sith to band together and defeat a more powerful Sith Master, with each Sith taking a portion of the Master's knowledge, weakening the order as a whole. Darth Bane solved this by creating the Rule of Two: one master to embody the power, the apprentice to crave it. That way the in-fighting would result in only the stronger Sith coming out ahead, leading to the advancement of the Sith as a whole. The results were successful since, even though it took over 1000 years, the Sith (under Darth Sidious) were able to defeat the long-standing incarnation of the Jedi Order.
Happens twice in the Honor Harrington series: the war between Manticore and Haven breaks out when the old People's Republic of Haven is an old corrupt oligarchy, continues when the oligarchs are overthrown by a populist revolution that becomes a dictatorship in the form of the new People's Republic of Haven, and still grinds on after a military coup which results in a restored democratic Republic of Haven.
This is also somewhat of an exception as The (People's) Republic of Haven is quite fleshed out, at least leading up to the second coup. Later books actually feature Havenite protagonists among the confusingly large ensemble cast.
See also the Levelers' Coup in A Whif of Grapeshot (where Citizen Admiral McQueen got her nickname of "Admiral Clusterbomb"), and of course The failed McQueen Coup. She didn't save Rob Pierre's government because she liked him, but only because the Levelers hated her as much as they did him.
One gets the impression that Havenite politics are a little rough and tumble by any standard.
Dark mages in the Alex Verus series seem to do this full-time. The books point out that it's a double-edged sword: the constant infighting means they're usually too busy with each other to gang up on anyone else, but by the same token it also means that the average Dark mage has a hell of a lot of combat experience.
The Riftwar Cycle has the moredhel , who are too busy with inter-clan wars to present a wide-scale danger to humans. In fact, the two occasions when the moredhel united completely under a single banner were quite memorable.
The Imperial Remnant in the Star WarsExpanded Universe fights among themselves almost at least as often as they do with the New Republic.
Grand Admiral Zaarin's and Grand Moff Trachta's actually attempted to usurp power from Palpatine during his reign. Neither succeeded.
This actually led to the crowning moment that turned Pellaeon from Thrawn's apprentice into his own Magnificent Bastard. He and Daala manage to get about 10 of the more powerful imperial warlords together and give them 1 hour to work out an alliance. When that (predictably) fails, they kill off all of the other warlords and instantly become the most powerful leaders of the Remnant.
Nom Anor and his constant machinations against the Yuuzhan Vong leadership. His revolution continued even after he abandoned it.
Admiral Niathal's betrayal of Jacen Solo...er...Darth Caedus. Niathal is a real vicious piece of work, and in the end, the best thing that could be said about her is that she has marginally higher moral scruples than an insane Sith Lord.
In J. R. R. Tolkien's The Lord of the Rings, all evil is ultimately under Sauron's control, but rivalry between Orc forces is still very common, as their race is literally Always Chaotic Evil. In The Two Towers, the constant squabbling between the Orcs from Isengard, Mordor, and the Misty Mountains eventually leads to their captives Merry and Pippin escaping, while in Return of the King, the Mordor Orcs of Minas Morgul and the Tower of Cirith Ungol decimate each other fighting over Frodo's treasure, allowing Sam to rescue him. It's also pretty clear that if Saruman had gotten his hands on the Ring, he'd have turned against Sauron in an instant, but thankfully that never came to pass.
In the book Saruman effectively betrayed Sauron as soon as he made it clear that he too was hunting for the Ring. Gandalf even comments how his task is easier at one point, because Sauron's eye is fixed on Isengard, instead of his activities. In the movie this double treachery doesn't seem to come to pass.
In the book, the eponymous Two Towers were Saruman's Orthanc in the first part, and Minas Morgul, in the second part. But because Minas Morgul isn't shown until the third movie, Peter Jackson had to justify the title by making Sauron's Barad-dûr the second tower. This meant he had to emphasize "the alliance of the Two Towers" and forget about Saruman's treachery.
In fact this is subverted with Mordor’s orcs: While Ugluk and Grishnak really were from different factions, the Mordor orcs work under the Nazgûl and some of them guard the path to Shelob’s lair and when the pressure from their superiors is enough, they fight themselves. Even so, Gorbag lampshades to Shagrat that they need to be together against the Free People:
But don't forget: the enemies don't love us any more than they love Him, and if they get topsides on Him, we're done too.
Red Harvest by Dashiell Hammett is this trope personified. A detective in an Outlaw Town decides to clean it up by stirring all the big criminals in town and their respective gangs into killing each other off. Considering they're very ill at ease with each other at any given time, this isn't very hard.
In the Dragonlance series the armies of the Dragon Highlords instantly dissolve into civil war when Ariakas is assassinated (at the instigation of one of the other Highlords).
In the Inheritance Cycle, besides the Varden, there's a tiny country called Surda that broke off from The Empire. By the second book, their king is actively funding and housing the Varden.
In James Swallow's Warhammer 40000Blood Angels novel Deus Sanguinius, the Warmaster and Inquisitor Stele dispute over their plans. Right up to the Warmaster, to rebuke Stele, tells his forces that Stele's ship is expendable.
At one point, in the Ciaphas Cain (HERO OF THE IMPERIUM!) book 'The Traitor's Hand,' Ciaphas is trying to stop a group of cultists from completing a Chaos ritual, when suddenly, Chaos Space Marines of a rival faction show up. These evil marines start killing the cultists, which Cain uses to plow a path to the main cultist headquarters.
The society of the Chaotic Neutral Kif from C.J. Cherryh's Chanur Novels is essentially a perpetual (but mostly cold) civil war. Everyone conspires against everyone. As soon as a leader overreaches, or shows signs of weakness, their alliance will quickly be taken over by a high level subordinate, or simply disintegrate.
In the Warhammer 40000Grey Knights novel Hammer of Daemons, the captive Alaric deduces that the lords of Drakaasi are barely tolerating each other, and instigates conflict between them as part of his escape plan.
In Ben Counter's Warhammer 40000 story "Words of Blood", Athellenas repeatedly attacks Chaos forces and retreats, despite his subordinates' hatred of the dishonor. By thus stoking their bloodlust and not letting them vent it on his Space Marines, he provokes them into fighting each other. When they go to clean up the survivors, the subordinates who preferred a Last Stand are fittingly humbled, and Athellanas explains the importance of victory — and realizes how important it was when he learns no one else could have helped the planet these forces intended to massacre.
Happens to Germany in the Alternate History novels Fox on the Rhine and Fox at the Front after the 20 July plot succeeds, Heinrich Himmler takes over, makes peace with the Soviet Union and sets Erwin Rommel on the Western Allies. After Rommel is captured by Patton the German Republic is formed and Rommel goes to war with Himmler.
In The Guardians, Lucifer holds the throne in Hell, but Beliel gained enough followers to fight him for it by promising to return them all to Divine Grace. Their war has been ongoing for millennia.
A recurring theme in Animorphs is that the Yeerk ranks often contain in-fighting, most notably between regular Big Bad Visser Three and the more calculating Visser One. There's also the Yeerk Peace Movement, which defies typical Yeerk imperialism by seeking a more symbiotic relationship between Yeerks and their hosts (although, as their name suggests, the Peace Movement doesn't do much fighting).
One of the advantages the Nations of the West in David Eddings' The Belgariad had is that despite the Angaraks being lumped together in their minds, they were really five different tribes and a bunch of client/servant races which rarely got along. Things really came to a head, though, when the Armies of the West go to distract the Angarak forces from what Garion, Silk and Belgarath are doing, only to find out too late that the Murgos and Malloreans would have just as happily beaten upon each other due to their rabid hatred of one another. And as an example that explains why the Mallorean Emperor was perfectly happy annihilating his fellow Angaraks, Murgo king Taur Urgas had ordered a girl Mallorean emperor Zakath had loved to assassinate him. Zakath had her executed, but did not realize until too late that she refused to perform the assassination. Much of the sequel series, The Malloreon is composed of a huge Mêlée à Trois between 'Zakath, Zandramas and Urvon for control of the Sardion, with Mengha and Agachak looking to get involved from the outside, and the Demons working for whoever summons them. Ultimately Mengha allies with Urvon (who he and Nahaz start plotting against), 'Zakath Heel Face Turns and Zandramas secures her position as the Big Bad with the deaths of Urvon, Agachak, and Mengha, and the banishment of Nahaz, in one of the most stunning examples of Eviler than Thou in fiction. Whew.
Happens again to a lesser degree in The Redemption Of Althalus. The protagonists are a tight-knit family who trusts each other, they have an actual Goddess actively working on their side, and their commanders and armies are loyal and efficient. They also have a house that can open doors to literally anywhere and is infinitely large, allowing all sorts of munchkin tactics. The antagonists are (intended to be) counterparts to the protagonists in all ways (including similar roles and powers), but they're openly distrustful and fight among themselves, actively encourage ancient and obsolete tactics and equipment (including flintstone weapons), command their soldiers through fear, their god won't help them very much at all, and their house is a hellish firepit that everyone is afraid of and won't use to its full potential. Is it just me, or did the Eddings have a fondness for stacking the deck?
Aside from the infinitely large house, every one of these points also applies to The Tamuli, although several gods are actively supporting the heroes here.
One of these is accidentally started in Red Inferno: 1945. A group of saboteurs led by an OSS agent use a stolen NKVD uniform to get close to the targets they are trying to destroy, purely because Soviet soldiers in general will let NKVD officers do whatever they please. But the general commanding the Soviet unit, once he learns of an NKVD officer destroying his supplies, assumes that the high command is trying to set him up for failure, because he is Armenian rather than Russian - an assumption he considers confirmed when one of the saboteurs uses the uniform to get close enough to try to assassinate him. Once recovered from his wounds, the general returns to his some country and starts a civil war against the Soviet Union, something that the saboteurs did not intend to do, but their superiors ultimately approve of.
Such haggling and wrangling I never heard. I'm nearly deaf. Aratus wished to cut out my heart, and Ivanos refused, to spite Aratus, whom he hates. All day long they snarled and spat at one another, and the crew quickly grew too drunk to vote either way-
In CetagandaMiles Vorkosigan works very hard to prevent the enemy Cetagandan Empire from breaking up, because he reasons that multiple Cetagandan warlord-states will be even more dangerous, rather like a tumor metastasizing. Instead of the relatively stable Cold-War type peace between the Barrayaran and Cetagandan Empires, each of the now-independent Cetagandan satrapies will start aggressively trying to expand.
Sisterhood series by Fern Michaels: Despite what some stories would have you believe, the bad guys are not happy working together. Indeed, a number of books in the series show that the bad guys are on the verge of this when the Vigilantes start gunning for them. When the Vigilantes capture them, this tends to break out with one of them spilling all the details, and then the bad guys start criticizing each other and their methods. Deadly Deals had this occur between Baron Bell and Adel Newsom, which Bell started by leaving her stranded. She then broke into his office, and tried to break into his safes, but she only succeeded at breaking into one and stealing the money in it. She tried to cut and run. It didn't matter, because Bell and Newsom got caught anyway!
In the Star Trek Mirror Universe novel Rise Like Lions, the Klingon-Cardassian Alliance begins to crumble in 2377 due to old animosities being stirred by the secretly telepathic Vulcan slaves and open conflict eventually erupts between the Klingons and the Cardassians, though it falls short of an outright civil war. Still, this lack of unity certainly is in the interests of the Terran Rebellion and Memory Omega.
Legacy of the Dragokin has many independent villain groups with alliances of convience that break apart when the alliances are no longer convenient. Indeed, the villains are just as likely to off other villains as the heroes.
The end of Season 2 in Buffy the Vampire Slayer: Angelus, Drusilla, and Spike have been working together, and Angelus plans to end the world by activating a demon that will suck the entire world into Hell. Whether because of Spike's jealousy about Angelus' winning Dru's attention or because of Spike's stated reasons of enjoying the world, he decides he doesn't want Angelus to end the world and cuts a deal with Buffy to help her save the world by betraying Angelus. This was long before Spike began his gradual Heel Face Turn.
In Season 4 of the reimagined Battlestar Galactica the 'human' Cylons are enmeshed in a Cylon civil war over the identities and whereabouts of their five missing models. When one of the Cylon raiders detects the presence of the missing models in the Colonial Fleet, the six remaining ones (Cavil, Leoben, Simon, Doral, Six and Sharon) are split, with the 'Rebels' (Leobens, Sixes and Sharons) in favor of searching for them and integrating them into their society whilst the other, 'Cavil' faction is opposed and set on enslaving their fellow machines lest they reveal any more. The irony of machines who rebelled against human bondage becoming 'human' and then putting their own machines in chains is not lost on the writers. All the models lose their ability to download. It transpires the missing five were earlier artificial humans who created the seven known models after the First Cylon War. A Colonial-Cylon alliance mounts an attack on Cavil and his followers. Eventually Cavil trades baby Hera to regain Cylon downloading technology and the war ends. Unfortunately a personal matter between two of the final five revealed itself during the handover in such as way that the agreement broke down, leading to the annihilation of the Cavil faction and miraculous survival of the Colonial alliance.
The Expanded Universe novels based on the original series (which were published before the new series premiered) also depict the Cylons having a civil war?between the (mostly) organic reptilian Cylons who founded the race, and the purely mechanical Cylons like the Centurions. Baltar, who has done a Heel Face Turn by this point, is literally tortured by nightmares of this war, due to his brain being cybernetically linked to the Cylon communications network (and unfortunately, said nightmares are the only way he can access the link).
Happens all the time in Stargate SG-1. The Goa'uld are feudal Always Chaotic Evil megalomaniacs by nature; the usual process is to fight among themselves until a top dog emerges (Ra, Apophis, Sokar, Apophis again, Ba'al, Anubis, Ba'al again...) then SG-1 wrecks the army of the top dog, and the cycle repeats itself. It's stated a few times in the series that the Goa'uld are actually doing more damage to their own forces than the puny Tau'ri; what Earth is really doing is continually upsetting the balance of power.
The Wraith in Stargate Atlantis, who are awakened prematurely before the human numbers in the Pegasus Galaxy have regrown, leaving them with low food supplies. Fortunately, the constant inter-Hive fighting helps keep the Wraith attention away from Atlantis. Then there's Michael...
The 1960s Doctor Who serial The Evil of the Daleks had some Daleks given human emotions, which turned them friendly, and sparked off a civil war which (supposedly) destroyed off every Dalek. Much later, there was an entire Story Arc in which Daleks loyal to Davros and to the Dalek Supreme, respectively, fought it out (Davros' side won). In the 1960s comics "The Dalek Chronicles", conflicts of this kind happened pretty regularly, with upstarts challenging the Dalek Emperor.
Farscape has a Gambit Roulette of the protagonists at the end of season 4 try to start one of these, by pitting the two Scarran slave-races against each other. Not even against the Scarrans. And this isn't even the plan, just a component of the plan. Yeah, Crichton was pretty nuts.
In the final run of Star Trek: Deep Space Nine the Cardassians realize that their alliance with the Dominion has reduced them to cannon fodder. It started out slowly, with just Damar and three Cardassian Orders, and started to build up, but it eventually led to a race-wide Heel Face Turn, giving the coalition forces a much needed opening for the final assault.
In Star Trek: Voyager the Q continuum (not really an enemy but the home universe of a pain in the neck) becomes engaged in a civil war that to humans looks like a reenactment of the U.S. civil war.
Later, the Borg also have one.
One Star Trek Expanded Universe novel reveals that the Romulans had one after the events of Star Trek Nemesis left a power vacuum. Senator Tal'Aura (you know, the one who actually murdered the rest of the Senate) has seized control of the Senate and is cracking down on any opposition, while a military-backed faction is seeking to depose her, headed by Commander Donatra (the one who fought Shinzon alongside Picard) and several high-ranking officers. Surprisingly, Admiral Tomalak is on Tal'Aura's side and successfully fights off Donatra and her fleet. While Tal'Aura wins this round, Donatra isn't done yet.
In the Super Sentai series Science Squad Dynaman, Prince Megiddo, initially a lackey, is imprisoned for his failure by the Emperor Aton and later emerges as mega badass Dark Knight (no, not that one) and ends up playing antihero for a while, then becomes the Big Bad himself after slaying Aton.
In The Sarah Connor Chronicles episode "Allison from Palmdale," Cameron tells Allison that she is working for a "pro-peace" faction within the machine army. This may have been a lie intended to find out where John Connor is, but Allison didn't play along in any case. A later episode suggests that there actually is such a faction, but when John sent a sub to contact them with an offer of alliance against Skynet, they turned him down.
This point becomes fleshed out in the finale when it turns out that Catherine Weaver's intention all along was to build an AI to fight against Skynet, possibly paving the way for a peaceful faction of machines to coexist with humans.
By the fourth episode of The Cape the eponymous hero has managed to provoke one between Scales and Fleming.
Despite Jesus describing Hell as united, it seems common depictions have many, many civil wars going on all the time. Lucifer himself, if present, usually isn't threatened; usually fomenting it on purpose to either consolidate his power or For the Evulz.
The Sandman portrayed hell this way. Morpheus' first visit had hell ruled as a tripartite kingdom between Lucifer, Beelzebub, and Azazel. By the second time he visits, Lucifer has wrested complete power for himself again, though it is implied he allows petty demon politics like that to happen to amuse himself. *
This wasn't Gaiman's intention but a mandate from DC editorial that he protested and detested so it would fit in with DC continuity where in another comic there was a triumvirate. Lucifer took power again simply because Gaiman decided to take a risk and ignore the editorial line.
C. S. Lewis' classic The Screwtape Letters manages to have it both ways. Hell holds together only because the lower (higher) ranks of the Lowerarchy are usually too powerful for minions to harm them. Bureaucratic backstabbing is a matter of course. After Screwtape's nephew fails to corrupt his assigned soul, Screwtape eats him.
All cases of artistic license. The Bible states that Satan and the demons are prisoners of hell, just as much as all the dead sinners. On the other hand, if you're more into the Tanakh, Satan works for God as a prosecutor.
In the myth of Jason and the Golden Fleece, Jason had to defeat an army of soldiers that had been created by planting dragon's teeth. He threw a rock at one of them, who assumed he had been struck by one of his comrades, and this started a fight which escalated until they all killed each other.
Dungeons & Dragons When not engaged in The Blood War, fighting amongst themselves is one of the most common ways for demons and devils to pass the time. For devils they are constantly seeking to usurp each other's position and Asmodeus in a recent edition orchestrated a revolution against himself for the purpose of exposing his enemies and humiliating them, while demons usually forgo the scheming and politicking and go straight into the massive bloodshed.
The Forgotten Realms campaign setting also has (or used to have) four other gods of drow that opposed Lolth, and a fifth that was technically subservient to her but had factions of his worshippers that were agitating to break away. All of them except Eilistraee were Chaotic Evil.
Also in Forgotten Realms, the forces of Zhentil Keep occasionally splintered into various cults of personality—most centered around the wizard Manshoon and the priest Fzoul—that led to frequent infighting. Also, after Manshoon's death, he was resurrected as a number of clones that all had the same memories, leading to a struggle between them known as the Manshoon Wars; this ended with three surviving clones, who managed to find ways to shut off the "Kill all other clones" psychoprogramming and resumed trying to rebuild Manshoon's power base (save for the one that housed Manshoon's real soul, who set about looking for a way to Body Surf between the clones).
To expand on the story about the revolution in Hell, known as the Reckoning: The King of Hell is Asmodeus; his two most powerful archdukes are Baalzebul and Mephistopheles. These two each wanted to rule Hell, so they gathered the remaining six archdevils into two factions that made war on each other, the winner taking on Asmodeus. When they had done enough damage to each other, one of the archdevils, Geryon, revealed he had been The Mole for Asmodeus the whole time and gave the signal for the legions of Hell to turn against their masters. In the end, all the archdevils were sent back to their domains, except Geryon, whom Asmodeus exiled for being blindly loyal to him—turns out being The Starscream is what Asmodeus expects of his vassals, and Geryon was the only one who was found wanting.
Completely off topic for this page, but recent information suggests that exiling Geryon for being loyal was just a front; Asmodeus is playing a Batman Gambit with Geryon to get him to do something that even the King of Hell can't be seen as being connected to.
This is specifically why the world isn't dead yet in the Old World of Darkness. Most notable is Mage The Awakening, where the Ancient Conspiracy known as the Seers of the Throne is constantly trying to keep its own groups from wiping each other out in power struggles and focus on the other mages.
Although it is never implied in the books, we must keep in mind these are devils, only a fool would expect one to be truly loyal, therefore Geryon's fate might be a lesson to other subordinates that everyone is disposable.
The factions of Warhammer Fantasy can be divided roughly into Order and Disorder, and since even the good races like the elves, dwarfs and Empire have had their share of civil wars, you can imagine what life is like among the others. Followers of Chaos compete violently amongst each other for the attention of their patron deities, the Skaven suffer from racial Chronic Backstabbing Disorder, and the Orcs and Goblins will just as eagerly fight each other than they would the other races - in fact, Greenskin armies have the Animosity rule that gives their troops a chance to ignore orders and shoot at a nearby friendly unit, squabble amongst themselves and do nothing for a turn, or surge ahead and try to get into close combat.
About the only race in Warhammer 40000 that isn't engaging in infighting are the Tau, and even they are trying to decide what to do with the separatist movement led by the renegade Commander O'Shovah.
The Imperium has suffered from numerous civil wars, from the disastrous Horus Heresy shortly after its founding to the more recent Age of Apostasy. At any given moment there's a dozen systems somewhere fighting a war of succession, especially given the breakdowns in communication and space travel at the close of the 41st millennium.
The only reason the Orks haven't conquered the galaxy yet is because they, like their Warhammer Fantasy counterparts, enjoy fighting each other as much as they do outsiders. Occasionally a strong-willed Warlord emerges to browbeat his rivals into following him on a Waaagh!, but such rampages inevitably end in Warbosses breaking off to start their own dreams of conquest - or power struggles over who should be Warlord.
Tyranid hive fleets have been observed battling with each other, but a true civil war is impossible as all Tyranids are controlled by the same Hive Mind. What's actually going on is that the "rival" fleets are testing the evolutionary upgrades they've accumulated against each other to see which is stronger - the "winner" absorbs the genetic advantages of the "loser" and recycles the dead bio-mass to produce more soldiers, so there is no downside to such battles.
Chaos, as befitting a faction represented by eight arrows going in different directions, is terminally fractious from top to bottom. The fourChaos Gods despise each other on a fundamental level and spend most of their efforts on wars in the Immaterium rather than the material plane. Meanwhile their mortal followers have not only inherited these hatreds but are also battling against rival champions of their patron deity, to prove they're worthy of their favour. Though at times the forces of Chaos have marched in step, like the Ork Waaagh! example above, such Black Crusades are merely temporary alliances between rival Chaos warlords that invariably end when their vicious rivalries resurface.
In Dan Abnett's Gaunt's Ghosts novel Traitor General, Sturm realizes that the warlord holding him intends to use him as a pawn in a struggle within Chaos for the post of Archon, after he lost that post in an open conflict. Indeed, Chaos agents attempt to assassinate him. It is also observed that the aforementioned conflict may have caused more casualties among the Chaos forces than the empire Imperial Crusade up to that point.
In Graham McNeill's Ultramarines novel Dead Sky Black Sun, there is fighting between two factions of a single Chaos Marine legion where Uriel arrives, and both sides are quite willing to use him against each other rather than stand united against him. Also, two major daemons of Khorne, apparently out of jealousy.
In promotional material for the Magic: The Gathering set New Phyrexia, it's suggested that the five Phyrexian factions' differing ideals may be sufficient to bring them down through infighting. Meanwhile, the Mirrans seem to have adopted a "now we are one" stance (a typically Phyrexian ideal), banding together to survive the corruption of their world.
The Xen invaders in Half-Life encounter the humans of Earth fighting each other, while both the Army and the scientistsGordonFreeman try to kill the aliens.
The same applies in Half-Life 2, with Xen aliens not only attacking both sides of the warring rebel humans and Combine soldiers, but also each other. Antlions are (even) more aggressive towards zombies than humans.
Largely because, with the exception of the Vortigaunts (who unanimously side with humanity), the Xen aliens are all just wild animals. Very aggressive and generally carnivorous wild animals.
There's an island called Warburg that was formerly under Rogue Isles (Arachnos) control, but became a splinter faction under the control of Marshal Blitz. Mechanically, this means that it's the only non-faction-based PvP zone in the game; villains can fight villains, and heroes can fight heroes.
The interdimensional invaders known as the Rikti are also split into the Traditionalists and the Reconstructionists. The first group eventually ally with the humans to stop the other from destroying the Earth after the true cause of the war is found out.
The tangled history of the Council and the 5th Column: The 5th originally split off from the Council, and many years later was violently reabsorbed. Requiem, the old leader of the 5th, has never been happy as part of the Council, plotting against his fellows and working to ensure the re-emergence of the 5th. Which has now happened, under a different leader, and fighting between the two groups has resumed.
Additionally, there have been occasional bugs where enemy groups (most recently, the Legacy Chain) have been hostile towards themselves.
The big one is the Great Schism (or the Covenant Civil War) in Halo 2, which results in a Strange Bedfellows situation between the Humans, the Elites, and some of the Grunts and Hunters who joined them.
The sequel Halo The Thursday War shows that events don't go as planned by ONI. The religious fanatics don't get enough support but still start the fight, but it looks like the Arbiter is going to win. However, the Arbiter then permits the above-mentioned team to enter a Forerunner relic on Sanghelios in order to retrieve a human scientist captured by the fanatics. This ends up turning the vast majority of the Sangheili against the Arbiter, and it looks like the fanatics may win in a very short while. This is also not the result ONI wants, as the fanatics hate the humans with a passion. Admiral Margaret Parangosky, the head of ONI, convinces Admiral Terrence Hood to bring UNSC Infinity, the fleet's newest flagship and the most powerful vessel in known space, to Sanghelios and rain Death from Above on the fanatics. However, in order to maintain the strife, ONI proceeds to destroy equal numbers of ships both those loyal to the Arbiter and the fanatics.
In Homeworld, the Taiidan empire is a decadent, despotic place. An incipient rebellion has been forming for some time before the game, but the appearance of the highly successful Kushan struggling to reach their eponymous Homeworld has emboldened them to resist and join the player's cause.
In Warcraft II, Gul'dan betrays the Horde on the eve of their victory by taking off with the Stormreaver and Twilight's Hammer clans to search for the Tomb of Sargeras. While this still left plenty of troops for Orgrim Doomhammer's siege of the Capital City of Lordaeron, Orgrim chooses honor over victory and sends the Blackrock clan, which constitutes a good third of the Horde forces, after the renegades. With the main Alliance army about to arrive and box him in, Orgrim is forced to call a retreat so close to victory. Furthermore, the battle between the renegades and the Blackrock clan results in the complete destruction or the renegade clans through sheer attrition (the orcs aren't known for their battle tactics). The seriously reduced Blackrock clan is further devastated by Admiral Proudmore's surprise attack at sea, leaving only a few thousand clan members alive. The war goes pretty much downhill for the orcs at this point. Even killing the supreme commander of the Alliance forces doesn't help, as Lothar's place is immediately taken by Turalyon.
The Orcs as a whole, who made up the bulk of the Horde in the days of Warcraft and Warcraft II, were serving as pawns of demonic controllers until they broke out of their bondage just before Warcraft III.
The Blood Elves originally split from the Alliance during Warcraft III: The Frozen Throne after deciding they'd had enough abuse from a racist Human commander. Later on, the Blood Elves had their own schism, after discovering that their leader and his forces defected to the same demonic controllers that had the Orcs under their thumbs.
Illidan's forces also split from the Burning Legion.
The Scourge were once the Burning Legion's second choice of pawns after they lost their reins on the Orcs. However, they too have turned against their demonic overlords.
The Forsaken are a faction of the Scourge who rebelled against the Lich King, reclaimed their free will, and now help the Horde fight their former undead fellows. It's arguable how "good" they are, as the race as a whole is at leastdark, with a few redemption/cure seekers, while others either actively bask in evil or revel in their undead natures.
The Forsaken later undergo another internal civil war during the World of Warcraft expansion Wrath of the Lich King, as traitors under the dreadlord Varimathras unleash the Forsaken's secret plague weapon against both the Scourge and against everyone attacking the Lich King, and nearly kill the Forsaken queen Sylvanas Windrunner to boot. This conveniently acts a cathartic experience to solidify the relatively "loyal" Forsaken to the service of the Horde, purging the nasty hints that have foreshadowed the race's untrustworthiness from the very beginning of the game.
Also, the Death Knights of the Ebon Blade. After being freed from the Lich King's control, the Death Knights vowed to take vengeance on Arthas and use their unholy powers against him. However, they're still met with distrust and fear by the other factions, and the Ebon Blade's interests don't necessarily coincide with their allies' at times.
One seems to be setting up for the Horde in Mists of Pandaria. With Garrosh passing the Moral Event Horizon by dropping a mana bomb on Theramore and only getting worse as time goes on, Baine and Vol'jin have begun expressing doubts about Garrosh. Vol'jin is later attacked by Garrosh's personal Kor'kron guard and left to die.Gallywix, meanwhile, seems intent to please Garrosh in Tides of War, and as of patch 5.1 the blood elf purge in Dalaran has pushed Lor'themar and the blood elves farther away from Garrosh than ever; in fact, in 5.2, Lor'themar is specifically looking for a weapon to use against Garrosh. It remains to be seen where Sylvanas and Ji Firepaw will end up in the conflict.
Looking at Tiberian Dawn and onwards (the Covert Ops expansion missions take place after GDI's victory), it is implied that if Kane isn't there, the Brotherhood falls apart. Which certainly proves true in Tiberian Sun.
The Nod campaign of Command & Conquer 2: Tiberian Sun starts you off fighting a Nod civil war. Only once you've beaten your rival does Kane return and then you launch your fight against GDI.
Then you get to Firestorm, where Kane's friendly neighborhood AI CABAL goes loopy and decides to wipe all of mankind - both GDI and Nod.
Tiberium Wars runs rampant with civil wars. Nod troops assault Temple Prime, apparently arranged to do so by a Nod loyalist trying to incriminate Kane's second in command for questioning his understandably obfuscating plans in private, then Kane turns around and orders the capture and execution of his own General Killian Qatar. In Kane's Wrath, the entire first act of the game is spent fighting Nod splinter factions.
From Nod's perspective, GDI experiences one in Tiberian Twilight when the player character's commanding officer tries to take down the elected government for perceived inaction against Kane.
The actual campaigns in Red Alert 1 are free of this, but it does show up in some of the missions in the expansion packs (the Soviets have a few missions against Allied-supported rebels/traitors still utilizing Soviet weaponry, and one conflict against a rogue faction of the USSR).
At some point in the Soviet campaign in both Red Alert 2 and Red Alert 3, you'll have to fight a traitor general/mind-controlling maniac. Even the Allies suffer a small civil war: you have to put down the power-crazy US president.
Subverted by the Empire of the Rising Sun in the base Red Alert 3 game. The first half of the Empire campaign even sets up a growing conflict between Yoshiro and Tatsu until the two men manage to reconcile their differences (Yoshiro's HeroicVillainous BSOD after learning the nature of Soviet Time Travel helped too).
In Star Control II, the main villain at first appears to be the Ur-Quan Kzer-za, a fanatical race who want to enslave all other life in the galaxy. As it turns out, the Ur-Quan species is split between the aforementioned Kzer-za and the even more extreme Kohr-ah, who instead want to kill all other life in the galaxy. And the Kzer-za were protecting you from them. And the Kohr-Ah are winning, because the good guys took out about a third of the Kzer-Za combat fleet in a recent war. Your first priority now becomes stopping the Kohr-ah
You can also cause a Yehat civil war between the Starship and the Royal clans. Subverted in that the Starship clans are friendly to your cause and will help you in the end.
The first level of Metal Gear Solid 4 takes place during a battle between rebels and a mercenary army, who will attack anyone who does not belong to their faction. While the mercenaries work for the Big Bad, they are only in the city because someone hired them, and the rebels really have no interest in Snake's mission at all.
You can use this to your advantage, too. If you start gunning down mercenaries or covering the rebels, they'll see you as an ally instead. This turns the first mission from a Stealth-Based Mission into a "enter the base completely unhindered and take all their items" mission.
Since Starcraft puts the player on all sides of the conflict, just about any civil war that happens in-game counts as one:
The Terrans of the Korpulu Sector have had tons of civil wars. The planet of Korhal rose up against the Terran Confederacy until it was nuked to glass, and the Sons of Korhal carried on the fight. When the Confederacy fell and the Sons of Korhal formed the Terran Dominion to take its place, remnants of the Confederacy formed the Confederate Resistance Forces, led by Samir Duran.
On the Zerg side of things, the player must at one point fight a rogue brood after its cerebrate has been murdered by the protagonist factions, while the expansion revolves around a massive civil war following the death of the Overmind.
For the Protoss, there's Tassadar's rebellion in the original, and then a brief relapse led by Aldaris during the expansion.
The Locust from Gears of War heads in this route, after the COG discover their enemies are waging the war on another front against their Lambent counterparts in Gears of War 2. The last game reveals this has been going on years before the first game; in fact, this trope was the whole reason behind the Human-Locust War, as the Locust couldn't find a quick enough solution to destroy the Lambent.
The Red Dragon Organization vs. The Black Dragon Organization from Mortal Kombat.
Jedi Academy has one mission with a situation like this, on the planet Yalara where Jaden is sent to destroy a cloaking device; he ends up in a three-way battle between him, the Imperial Remnant, and some alien assassins Darth Vader had left there years before.
The dark side ending of Academy is also a three-way war between the Jedi, the Dark Jedi, and the evil player. Which itself was kind of a ripoff of the original Jedi Knight, in which the dark side ending is still a war between the player and the Dark Jedi, except the player's also a Dark Jedi.
If you maxed out Mind Trick, which at its highest level converts a non-Jedi enemy to your side for 30 seconds, it's also possible to create an Enemy Civil War simply by performing Mind Trick on half a roomful of enemy mooks.
And in Outcast, Fyyar intends to overthrow Desann. Of course, the guy was insane.
The Punisher has the Yakuza mook-army attacking the various factions that the Punisher has weakened. In one moment in the Kingpin's lobby, just wait in the elevator until the Yazuka has weakened the Kingpin's security forces.
In Diablo, two lesser demon lords made a pact to overthrow the three greatest ones in one civil war, and afterward they started another civil war between them.
And then it's revealed in Diablo II that the three greater demons masterminded the whole thing in order to get themselves exiled to the the human world.
Done more simply in Doom games. Get a monster to hit another of a different species, and bam, fight to the death. Then you shoot whichever one survived, weakened.
In The Suffering, the monsters will sometimes attack each other. Unlike Doom, they don't have to hit each other, or even be particularly close. It's not just entertaining, it helps drive home the idea that the monsters are literal incarnations of hate and rage.
In Mass Effect 2, the player learns that the Geth are split into two factions: the main "True" geth that have no real hostility towards organics and sent Legion to help you, and the splinter-faction "Heretics" who follow The Reapers and are the ones you fought in the first game. You're later able to resolve this by reprogramming the Heretics to return to the True Geth or destroying the majority of the Heretics.
This goes back to before the first game, as revealed in the Expanded Universe novel The Calling, which first introduces the Architect, who is leading a faction of the Darkspawn (more like mind controlling) to stop the constant struggle between the Darkspawn and the other races through extreme means. They are not shown to be fighting amongst each other, though.
Civilization II played this trope incredibly straight, in a way. In a war, if you captured the enemy's capital and they were sufficiently large enough or advanced enough, the civilization would split into two factions who would then immediately declare war on each other. While in a couple of turns they would establish peaceful relationships, this was a very powerful way to mess up stronger civs.
This appears in several games in the Total War series, at least from the perspective of other factions:
In Medieval: Total War, a faction who's royal family was destroyed, or who possessed a particularly weak monarch, could suffer rebellion as rival claimants attempted to seize the throne for themselves.
In both Medieval and Medieval 2, Catholic factions who have been excommunicated may suffer from widespread hostility from Papal loyalists, which can be seen as an Enemy Civil War from the perspective of any Muslim factions holding the Holy Land at that point. When the French are sending crusaders to Frankfurt, they're not sending them to Jerusalem...
The Barbarian Invasion expansion to Rome also featured possible civil wars in the Eastern and Western Roman Empires, as well as the division of the Gothic faction into Ostrogoths and Visigoths.
Empire includes emergent factions which can emerge into dissatisfied regions of an existing faction, e.g. Ireland, Scotland and the United States may rebel against British rule.
The Archers from Assassins Creed II will attack anyone on a roof who isn't another guard. This isn't limited to Ezio or thieves, but also pickpockets and Borgia Couriers, who are also enemies of Ezio. In Bonfire of the Vanities you will see guards fighting each other even though both sides appear as red, i.e. hostile, in Eagle Vision.
Can be invoked in Assassins Creed Revelations. Ottoman and Byzantine Templar guards will get into fights if they see each other, and one tutorial specifically tells you to make use of this.
Storywise, happens frequently in Sword of the Stars with the Hiver race between the many Princesses vying for power (from the viewpoint of another race, of course). Also entirely possible with any race, as brilliantly worked into the backstory by Arinn Dembo, the game's writer. Humans, as we know, can easily split into factions and fight amongst each other for trivial reasons. The same is true for the Tarka. The Liir will fight anyone they believe has become Suul'ka, even members of their own race. Which makes a lot of sense in light of the sequel revealing exactly what the Suul'ka are. The Morrigi have never been a unified species. The Zuul, being religious fanatics, worship their creators; and, of course, no one has ever split into factions if they believe in the same deity.
In an interview at the announcement of Sword of the Stars 2, Arinn Dembo revealed that the Zuul will split into two factions: the ones who follow their evil masters, and the ones who choose to side with the other races against them. Specifically, they're allying with the Liir.
Specifically, the Prester Zuul have renounced their faith in the Great Masters, and many of them have turned to Catholicism. Several Zuul are fully-ordained Catholic priests, by the way. They also have begun to use their Mind Rape powers for good, specifically, to excise violent memories from Liir spacers, which usually cause them to go insane after a while.
Can occur in Conduit 2 when aliens of opposition factions engage each other.
Iji has the Tasen-Komato War, which is central to the plot.
In The Elder Scrolls IV Oblivion, you may occasionally happen upon two Imperial Foresters (who can be "enemies" depending on how lawless you are) trying to kill each other. This is because Foresters need to hunt for food and will often kill deer. However, deer are marked as friendly towards Imperial Legionaries, so this is considered murder if witnessed by any other Legionaries, who will move in to arrest the "murderer". However, Legionaries aren't programmed to be arrested since they don't normally break the law, so they automatically resist arrest and a fight begins.
Crusader Kings 2 has this happen on an extremely regular basis. It's quite likely a faction that's under a lot of military stress will begin to fragment as dissatisfied vassals decide to make a play for independence. Also, if you want to get really broad with your definition of a civil war, it's not uncommon for wars between Christian kingdoms to severely weaken the forces available for a crusade. This is less common for Muslims, as both their Caliphs are part of extremely powerful kingdoms, but occasionally there will be a ill/well timed throwdown between Sunni and Shia Muslims.
8-Bit Theater is a Villain Protagonist example, with the Light Warriors (Black Mage and Thief especially) constantly plotting against and attempting to betray/maim/kill each other. Unfortunately for the planet, they are fairly united when causing others suffering as well.
Dominic Deegan had the War in Hell arc, which started with the mass destruction of a gigantic cult known as the Chosen. All of the Demon Lords turned against each other and threw their mortal Infernomancers into the fray; while Dominic was loath to do it, he supported Karnak (who, his Infernomancer having been banished, was at a disadvantage) because it was a literal case of "the devil you know". Karnak ended the war by hurling a spear through the massed souls of the Chosen - when a soul is destroyed in the Deeganverse, it explodes, and this set off a chain reaction that killed all the other Demon Lords and tore Hell to shreds. He then pronounced himself King of Hell, as all other candidates were dead.
Something more like an enemy cold war exists between Xykon and Redcloak in The Order of the Stick. Though Redcloak is largely incapable of betraying Xykon outright because he feels if he does, the death of his brother will be in vain he doesn't particularly like him either, and will freely use him for his own ends and hide information from him. Recent events suggest this is now mutual, with Xykon no longer trusting Redcloak to hold up his end of the bargain and (possibly) grooming another minion to take his place. However this winds up playing out, it won't be pretty.
In Sluggy Freelance, the board members of Hereti Corp aren't above conspiring against each other for sometimes very petty reasons. There are also at least two demons (Skip and Chilus) who, while both being K'Z'K worshipers, have very differing takes on how K'Z'K's conquest of Earth should be brought about. Made more complicated since K'Z'K himself is apparently dead.
In The Gamers Alliance, the four demon hordes of Yamato want to take over the world and enslave "lesser beings", but their grand plans are hindered because they also fight brutally against one another for power after the Cataclysm. Duchess Vaetris intends to change the status quo, however, by uniting the bickering hordes under one banner in order to amass a large enough, united force which she can use to finally take over the world.
In Sailor Nothing, this is arguably the only reason the good guys won. The entire Yamiko RACE was against itself, too distracted by their own individual dark desires to accomplish anything that didn't immediately and personally benefit them, and the few Yamiko that weren't too blind to realize this wanted to die and/or wipe out their own race.
Tech Infantry sees the Earth Federation constantly going through an endless series of rebellions and civil wars. Whether the Earth Federation are the good guys or the bad guys is very much dependent on which character you ask.
In There Will Be Brawl, the ongoing territory struggle between Bowser, Ganondorf, King Dedede, and the now-dead Mewtwo serves as the basis for the plot. Divided We Fall are the Mushroom Kingdom and the annexed, mostly corrupt Kingdom of Hyrule.
In Protectors of the Plot Continuum, the death of the Yarrow sent the League of Mary Sue Factories into a power struggle between the Forget-Me-Not and the Venomous Tentacula. The latter won.
Humanity benefited from this during the invasion of Hell in The Salvation War, for several thousand years of Chronic Backstabbing Disorder at the Deadly Decadent Court meant the various dukes and barons of Hell were more interested in currying favour with Satan and watching their own backs than reacting to humanity's military successes. This cultural trend has not abated significantly now that the invasion has become an occupation, however, which will undoubtedly create problems in the long run. And quite what Michael-lan is up to in Heaven is anybody's guess.
What finally brings down the Soviet Union in Red Dawn Plus 20, preceded by a mass assassination of the Soviet Politburo.
This is a very common element in any Transformers series.
Firstly, Starscream, Blitzwing, and Astrotrain perform a joint coup against Megatron; however, the two Triple Changers double cross Starscream, trapping him with Megatron. Later, they start fighting each other, after which the Constructicons turn on Blitzwing, resulting in at least four factions fighting among themselves.
Then, after Megatron finally exiled Starscream, ol' Screamer returned and successfully wrested control away from Megatron with the help of the Combaticons; he was only defeated when the Stunticons decided it would be worse if Starscream was in charge than Megatron.
Then the Combaticons defected from Starscream and conquered Cybertron, forcing Starscream and Shockwave into a Strange Bedfellows situation as they both tried to regain control of the planet while not trusting each other in the slightest.
Beast Wars and Transformers Animated both have plenty. Notably the latter for a long time had Megatron commanding a grand total of two Decepticons on Earth.
The Insecticons ended up fighting against the rest of the Decepticons almost every single time they appeared.
The second season finale of Transformers Animated was a giant clusterfuck battle between the respective followers of Megatron, Starscream, and Optimus Prime.
In the penultimate episode of the series, the Legion of Doom splinters apart when Gorilla Grodd and his supporters mutiny against Lex Luthor. It ended up being one of the best episodes of the series, and unlike several other episodes with this trope, it is notable for not actually featuring the heroes until the very end when Darkseid returns.
In "The Ties That Bind", it's revealed that Apokolips had fallen into one of these since the death of Darkseid in Season 2 (Pre-"Unlimited"). Of course, as soon as Darkseid comes back, that civil war grinds to an instant halt.
In the Secret Wars arc of Spider-Man: The Animated Series (based on a comic story arc of the same name), the villains which the Beyonder sent to Battle World to represent the team of evil all considered conquering the other villains more important than dealing with the heroes. Even when Dr. Octopus and Red Skull agreed to work together to defeat the heroes and Dr. Doom, the two constantly mentioned plans to backstab the other the moment Doom was out of the picture.
Young Justice features one between Kobra and Bane's forces in "Drop Zone".
There is one in The Avengers: Earth's Mightiest Heroes between HYDRA and AIM. Both are fighting over the cosmic cube. Neither acquire it and the leaders of both, along with their surviving troops, are arrested.
In the first season of Avatar The Last Airbender, it is established in the third episode that Zuko has a rival in his search for the Avatar; Zhao, a Fire Nation commander who wants the glory of capturing the Avatar for himself. The two try to sabotage each other at multiple points, culminating in Zhao trying to kill Zuko.
Any civil war ever has been seen as this by someone. It's all about your point of view.
Western intel groups like the CIA figured that this trope would keep Sunni (like al-Qaeda) and Shi'a (like Hezbollah) terrorist groups from ever working together. Sometimes it works, sometimes it doesn't.
As of May 1, pundits are now speculating whether al-Qaeda's various nationalist factions will start invoking this trope over who'll inherit control of the terrorist network.
Iran never liked the various forces backed by the US during the Cold War, which included secular Iraqi dictator Saddam Hussein as well as the fundamentalist anti-Soviet Taliban of Aghanistan. The War On Terror is a blessing for them in a way that no one expected: the US is bogged down fighting the myriad factions in Iraq and the Taliban remnants in Afghanistan, leaving the US unable to harm Iran in any meaningful way.
Syrian dictator Bashar al-Assad is locked in a deadly war against the rebels, which are backed by various foreign interests. However, the rebels are not a united force: some of them openly pledge loyalty to transnational fundamentalist force that is al-Qaeda, and some of them are backed by Western and/or GCC countries. Understandably, the fundamentalists are not willing to let foreign infidels into Syria while the Western countries are not willing to "hand the guns to the terrorists"note They did this during the toppling of Libyan dictator Gadafi, the al-Qaeda elements of the Libyan rebels then send the guns to Mali.. The rebels end up fighting each others as much as they fight Assad.
Both sides in the Jewish-Roman War of 66-73 AD (the one that destroyed the Second Temple). The Romans were fairly united until around 68 or 69 when Nero's death led to the Year of Four Emperors, but they got things settled pretty quickly. The Jews, on the other hand, spent most of the war fighting each other as much as the Romans. The biggest split was between those who wanted to fight to the death and those who wanted to surrender.
As America and its NATO allies fought the Eastern Block during the Cold War, China tried to replace the Soviet Union as leader of that movement.
The IRA, that being the original IRA, the anti-treaty IRA, the Official IRA, the Provisional IRA, the Continuity IRA, the Irish Republican Liberation Army, Irish People's Liberation Organisation, Republican Sinn Féin and the Real IRA; this was the source of the parody in Monty Python's Life of Brian.
Any time the British security services went up against the Ulster Defence Volunteers must have counted from the IRA's point of view, though the official line was always that the latter was an illegal organisation.
The Republican side in the Spanish Civil War. One of the main reasons why the Fascists won was that Communists and Anarchists were on each others' throats and the Communists fought the Anarchists with equal fervour they fought the Franquistas.
Inverted in much of Europe at the end of World War II. Once it was clear the Germans were going to be defeated, the left-wing resistance movements took the opportunity to turn on their real enemies: the right-wing resistance movements (or vice versa).
Historically, most successful revolutions are followed by at least low-key civil wars. Even the USA had the Whiskey Rebellions.