You are an EvilOverlord who has just conquered another place, crushed the puny [[LaResistance resistance]], set up the proper [[ReignOfTerror measures to keep people in line]] and are ready to spill more blood for the blood god. Instead of simply annihilating the conquered enemy's armed forces, you have a much more efficient solution: add them to your own army. LesCollaborateurs may serve as the sergeant to this new army, but often it is headed by a [[FantasticRacism Fantastic Racist]] who will rarely show much mercy for this battalion.

There are several regiments of the Battle Thralls:
* ProudWarriorRaceGuy: This branch consists of a group of people who believes that might makes right. Because they were beaten in combat, they accept their new leader and will not question his authority. Their new leader is a source of enlightenment, and serving him is their highest honor. However, any who feel their honor has been insulted will gladly [[EnemyMine join with,]] or at least be neutral towards, the rebels. Those who do join LaResistance usually seek to regain their group's lost glory. In battle, they are often both strong warriors and skilled strategists.
* Barbarian Marauders: Brutish, wild and dumb. The Barbarian Marauder is perfectly fine with serving under the new EvilOverlord. He may terrorize the empire's enemies, but he usually fights for little more than his own amusement. Basically, sociopaths pointed in another direction. Their brutality is offset by their simple-mindedness. If their hedonistic needs are not met, they will pick apart your empire bit by bit.
* Engineers of Doom: They are responsible for preparing the empire for war. They rarely take sides in the conflict, only working to make sure the war machine is running. They will only fight the rebels if absolutely necessary. They are often the straight man of the Battle Thralls, being the voice of reason that prevents the Chaotic Evil and Lawful Evil groups from killing each other. If the opportunity is given to rebel, they may offer a token of assistance to the heroes but will usually refrain from directly sabotaging the empire's infrastructure.
* Taskmasters: [[DrillSergeantNasty Drill Sergeants Nasty]] UpToEleven. They're the guys that stand behind all the SlaveMooks and whip them into shape. Though they usually outnumber the Taskmasters, harsh punishments, indoctrination and fear tactics will make sure that the SlaveMooks will rarely rebel against them.
* [[SlaveMooks Enslaved Grunts]]: The lowest rank of Battle Thralls, basically rounded up and given a crude weapon or bomb. They are usually employed in a ZergRush against their enemies. They are regarded by both sides as target practice and friendly fire is often an issue. They rarely have the courage to stand up and fight against their overlords. If not "freed" by the rebels, they often realize that their lot in life is to die anyway and thus may sacrifice themselves for the emperor, no matter how hopeless the attack is.
* Sneaky Mercs: Thieves, bandits and other lowlifes who are more than willing to harm a helpless target but flee at the first sign of danger. Their role in combat is to act as the surgical knife of the lowlifes, stealing from, sabotaging, or terrorizing their enemies. They may boast about the fact that the empire has allowed lowlifes such as themselves to live instead of executing them.
* Dogmatic Drones: Robot Mooks, a dogmatic drone army made of faceless robots united under a single leader, who either created them or gave them a purpose. Often in the LawfulEvil territory. They act as a deadlier version of a ZergRush. Unlike grunts, they generally don't have rebellious tendencies. Those that do rebel or otherwise break away from the main contingent are considered "defective".


[[folder: Anime and Manga]]
* ''Manga/{{Berserk}}'':
** Enslaved Grunts: The Kushan Empire uses captured enemy soldiers as frontline CannonFodder: They'll get killed if they try to run away, while the enemy may have difficulty shooting their countrymen.
** The new Band of the Hawk pulls a reversal on them: Kushan soldiers defeated but not killed by them are thrown on the front lines in a similar manner. However, those that manage to survive three battles are offered the chance to swear their loyalty to Griffith and, if they do so, become full members of the Band of the Hawk. A lot of the Kushan consider this better treatment than they received [[BadBoss under Ganishka]].
* In ''Manga/OnePiece'', Hody Jones's New Fishman Pirates is partially comprised of human slaves fitted with explosive collars. If they do not fight, they are blown up.
* In ''Anime/CodeGeass'' Lloyd, "the earl of pudding" is an Engineer of Doom. Actually he is only interested in machines and doesn't really care much about humans.
** An army of Enslaved Grunts pops up late in ''Anime/CodeGeass'', [[spoiler:controlled by Emperor Lelouch's Geass as part of a deliberate play at ZeroPercentApprovalRating right before pulling a SilentScapegoat.]]
* Several of the various [[AlternateContinuity Alternate Continuities]] of ''Anime/CaptainHarlock'' have the {{Big Bad}}s employ conquered races in their forces; Harlock himself is sometimes [[DefectorFromDecadence turning his back on]] [[VichyEarth a homeworld all too eager to join the ranks of the Battle Thralls that helped conquer it]]. Most of the other Thralls in the franchise are mixes of Enslaved Grunts and Proud Warrior Race Guys.
* ''Anime/SpaceBattleshipYamato2199'' uses this trope to perform a CerebusRetcon of how the original changed the skin color of the Gamilas (Gamilons for ''Star Blazers'') after the [[SortingAlgorithmOfEvil first few enemy commanders were defeated]]; the new version has members of other conquered species serving in the Gamilas military. Note that these guys are all volunteers: some have enrolled because their worlds have been culturally assimilated and they're patriots, while others want the first-class citizenship that comes for them and their families once they complete the term (or honorably die trying).

* ProudWarriorRaceGuy: Mandalorian Clone Troopers in the ''Franchise/StarWars'' ExpandedUniverse. (Some Clone Troopers who valued their roots then to the Republic and later the Empire).
* In the ''TabletopGame/{{Warhammer 40000}}'' background book ''Xenology'', the Ethereals are hinted to have turned the Tau into Battle Thralls for the Eldar since their innate warp resistance meant they can't be controlled by Chaos nor be wary of being manipulated by the Eldar. The source was poetic and symbolic, spread over sources from two races on opposite sides of the galaxy; the interpretation of the text as referring to the Eldar was in-universe and it could equally apply to the Dark Eldar and human-looking Necron infiltrators (which feature heavily in the book.)
* In the ''Literature/BelisariusSeries'' the Rajputs and Kushans are ProudWarriorRace guys; both of them defected though the Kushans defected earlier (the Rajputs had to be left so that Belisarius would have someone decent to fight through most of the plot). These two are more {{Worthy Opponent}}s than the rather grim jackboots described above; the Rajputs are aristocratic warriors and the Kushans tough professionals, not totally unlike Romans. Their skill at siegecraft makes them Engineers of Doom as well as a ProudWarriorRace The Ye-tai are barbarian marauders; while brave enough, they tend to be uses as taskmasters, driving the conscripted peasant grunts whose main purpose seems to be to get killed one way or another. The sneaky mooks appear as well in the form of assassins which range from street thugs to ninja-like badass [[StealthExpert Stealth Experts]]. Interestingly, the last are what Link seems to trust must.
* The [[TheEmpire Seanchan]] in ''Literature/TheWheelOfTime'' capture and [[SuperHumanTrafficking enslave female magic-users]] with [[AuthorAppeal enchanted leashes]] that [[MindControl enforce obedience]] and use them in combat. They [[FantasticRacism consider them]] more like {{Attack Animal}}s than this trope.
* In ''Literature/RanksOfBronze'' the Galactic Federation allows trade guilds to start wars to secure predatory trade deals with low-tech planets, but they can't use weapons more advanced than those of the natives. So one guild obtains an enslaved Roman legion and makes them fight for them. They seem like [[HumansAreWarriors proud warrior race guys]], but they attribute their own repeated successes to their discipline as [[SoldierVsWarrior soldiers]].
* In the Cross-Time Engineer series by Creator/LeoFrankowski, the Polish gunboats with SteamPunk weaponry are massacring the Mongol invaders trying to cross the river Vistula, but they just keep coming. The Poles assume the Mongols are NotAfraidToDie, as a Mongol ambassador ordered several of his men to cut their own throats just to prove this point. What they don't know is that the enemy commanders are using Polish prisoners and soldiers from nations they've already conquered as CannonFodder.

[[folder:Live Action TV]]
* ''Series/StargateSG1'': Kull Warriors are Dogmatic Drones of the SuperSoldier variety, and until a weapon specifically made to kill them quick was developed, also very [[ImplacableMan hard to stop]].
* ''Series/FallingSkies'': In season 4 the Espheni started a new program in converting human children into soldiers, by placing them in reeducation camps and convert them into Espheni. Later they created a new weapon which slowly converts humans into Espheni.
* In ''Series/StarTrekDeepSpaceNine'' this is generally how the Dominion works. The Founders are the head of government and instruct the Vorta (the only solid race they actually trust) to perform diplomatic and administrative tasks. Vorta in turn are given control over the Jem'Hadar, shock troops who are less diplomatic about enforcing the Founder's will. Both are fanatically loyal and see their service to the founders as their greatest duty (they see them as gods). Interesting, most races view the Jem'Hadar as more trustworthy as they have a code of honor, and the Vorta as scheming and superficially respectful. Within the Dominion itself, most clients don't know anything about the leadership of the Dominion beyond that the Vorta are the deal makers and the Jem'Hadar enforce the deal.

[[folder:Tabletop Games]]
* In the ''TabletopGame/DungeonsAndDragons'' Dark Sun setting, Enslaved Grunts come in both slave soldiers and gladiator varieties.
* Clan Warriors in ''TabletopGame/BattleTech'' are {{Proud Warrior Race Guy}}s who are expected to, if captured in battle, serve their captors as bondsmen and women. Often they are made Warriors of their capturing Clan and this practice enables Clans to add new genes and Bloodnames to their gene pools. This caused some confusion when they invaded the Inner Sphere, whose major powers typically return prisoners of war to their home nations at the soonest possible convenience.
* ''TabletopGame/WarhammerFantasy'':
** The Chaos Dwarfs use orcs and goblins in this role, since they don't have enough Dwarfs to fill out their army, with [[LesCollaborateurs hobgoblins]] serving as Taskmasters.
** The bulk of the Skaven armies are composed of slave rats from other Skaven clans that were conquered. They are mostly used as CannonFodder and their masters have no problem shooting [[UnfriendlyFire with their own weapons]] (not that they wouldn't do the same to their own grunts).
* The Abyssal Dwarfs in ''TabletopGame/KingsOfWar'' use orc slaves and demonic gargoyles to boost their numbers.

[[folder:Video Games]]
* ''VideoGame/StarControl'' is the TropeNamer with the Hierarchy of Battle Thralls led by the Ur-Quan Kzer-Za, although you learn more about them in ''VideoGame/StarControlII''.
** ProudWarriorRaceGuy: The Thraddash. Possibly overlaps with the Barbarian Marauders (they're proud, but also dumb as bricks and unapologetically violent to a fault). The Yehat in ''Star Control II'' are a more straight example; being classic Proud Warrior Race Guys who serve the Ur-Quan Kzer-Za willingly under orders from their Veep-Neep Queen; in the first game, the Yehat were part of TheAlliance of the Free Stars.
** Barbarian Marauders: The Ilwrath. They live for evil and became Battle Thralls to the Ur-Quan Kzer-Za solely for the purpose of obtaining sacrifices for their dark gods. The VUX are a bit of a subversion; they're intelligent and very eloquent, they're just narcissistic as heck and are heinously violently solely because they consider every non-VUX lifeform (humans especially) in the universe uglier than they are.
** Engineers of Doom: The Umgah. Pranksome geneticists that can be helpful if you can figure out why they're so quirky.
** Enslaved Grunts: The Spathi, a race of cephalopod cowards. The Mycon might also apply here, in the "living bomb" sense - they joined the Ur-Quan Slave Empire in order to gain new worlds to terraform by burying their children into its crust.
*** In general, Kzer-Za policy limits the slave part of it -- a race becoming Battle Thralls is supposed to be a choice ''by that race'' (with the alternative being Slave Shielding), but the choice is final... even if an Umgah practical joke made you think you were choosing to be Slave Shielded.
** Dogmatic Drones: The Mycon are the unholy combination of {{Planet Eater}}s and a HordeOfAlienLocusts.
** The backstory reveals that [[spoiler:the Ur-Quan themselves were Battle Thralls for the Dnyarri millenia ago. The green Kzer-Za were Engineers of Doom while the black Kohr-Ah were Enslaved Grunts. The reasoning behind the Ur-Quan's enslaving or killing of other species is to ensure that this ''never'' happens to them again.]]
* ''VideoGame/TotalWar''
** ''VideoGame/ShogunTotalWar'': The Mongol's basic, cheap infantry units from the ''Mongol Invasion'' expansion are basically Korean captives/vassals pressed into service.
** You can recruit thralls in the ''Viking Invasion'' ExpansionPack for ''VideoGame/MedievalTotalWar''.
** In ''VideoGame/TotalWarAttila'', you can recruit troops from either vassal states or (if you're a Roman empire) from friendly tribes passing through your territory. Also, many of the Persians' default units are (in the fluff) troops raised from particular regional cultures.
* In ''VideoGame/WarriorsOrochi'', the Wei and Wu became LesCollaborateurs and BattleThralls with Orochi
* Yuber from ''VideoGame/{{Suikoden}}'' is a mix of Barbarian Marauder (he destroyed a whole village because he was bored while waiting), Enslaved Grunt (he can be summoned and will work for the ones responsible for doing so.. at least until he's in danger) and Sneaky Merc (he actively seeks, craves and creates chaos and participates in most wars. However once he feels that he is in danger he will flee, usually by teleporting, and abandon the squad he was commanding and the battle he was fighting).
* ''Franchise/{{Halo}}'''s Covenant has most of these, with the Prophets in charge:
** The Elites (Sangheili) are the Proud Warrior Race Guys, of course. The Brutes (Jiralhanae) are the Barbarian Marauders. The Grunts (Unggoy) are, well, the Enslaved Grunts. The Jackals (Kig-Yar) are the Sneaky Mercs. The Drones (Yanme'e) are, you guessed it, the Dogmatic Drones (though an organic insectoid form of such). And the Engineers (Huragok) are, naturally, the Engineers of Doom.
* ''VideoGame/ValkyriaChronicles'': the battle thralls make up a significant part of TheEmpire's military might. Some of them even rise to become the Imperial nobles' right-hand men, such as Radi Jaeger.
** Darcssen finds a special niche amongst Europan battle thralls: as engineers of doom. Just look at the [[VideoGame/ValkyriaChroniclesIII Calamity Raven]] and their advanced death-machines. Heck, even ''[[TooGoodForThisSinfulEarth Isara]]'' technically is one: without adoption by the Welkins or her inventions, she would never be considered a full-fledged citizen of Gallia.
* In ''Franchise/DragonAge'', the Qunari give their mages, whom they call "Saarebas" or "dangerous thing", this treatment after it becomes apparent that they can't ignore the advantages that magic brings to the battlefield. They are chained up like animals and are kept on a leash with special control rods.
* Both ''VideoGame/XCOMEnemyUnknown'' and ''VideoGame/TheBureauXCOMDeclassified'' feature the main aliens (the Etherials and the Zudjari/Outsiders, respectively) using several other alien races that have previously been conquered by them. The final ''EU'' mission has the BigBad give you a bit of background on each alien race, claiming they have been conquered and turned into loyal soldiers ([[spoiler:by virtue of implants and mind control]]). ''The Bureau'' only really features two conquered alien races being used in combat. The Sectoids are clearly wearing some sort of control collar, and all aliens appear to be jacked into [[HiveMind Mosaic]]. One cutscene has an Outsider playfully administer a PsychicAssistedSuicide on a Sectoid. Also notable that the two battle thrall races in ''The Bureau'' (Sectoids and Mutons) appear to be nearly identical to their ''EU'' versions, at least physically, although the ''EU'' Sectoids are all clones. In fact, [[spoiler:the goal of both BigBad races is to turn humanity into their most promising BattleThralls yet]]. Or turn humanity into BigBad clones/spare bodies.
* ''VideoGame/TheWonderful101'': TheRival does this to individual champions of 100 different planets, threatening to destroy a world if the champion ever turns traitor or gives up. Interestingly, he has a very high opinion of his minions ("100 of the galaxy's finest") but is too worried that they'll just up and leave the moment their homeworlds are safe. They do, but not before helping him and Centinel save the galaxy from the GETHJERK.
* In ''VideoGame/GemsOfWar'', one of the troops associated with Darkstone is the Thrall; they're presumably not happy to be fighting, and their special move actually hurts them (in addition to other effects).
* ''Videogame/{{Stellaris}}'':
** If your empire allows slavery, you can conscript your slaves into Slave Armies, which generally work best when under the watchful eyes of [[ThePoliticalOfficer Comissars]] serving as the Taskmasters.
*** The "Utopia" DLC has Battle Thralls as a specific type of slavery that reduces their food and mineral production (the usual benefit of slaves), but they're more content with their lot in life than other types of slave.
** You can also use 'vassalage' as a peace demand in your wars, which means you can build up an empire of Battle Thralls who you invaded and who very possibly loathe you but nevertheless send fleets to support your future war efforts. The achievement for subjugating three empires in this way is even called 'Battle Thralls.'

[[folder:Real Life]]
* Near the end of its reign, Rome, the classic VestigialEmpire, was hiring a lot of barbarians, because its own army was depleted. They even hired the Huns at one point to take down the Burgundians. The Huns quickly figured out there was a lot more gold where their paycheck came from, and spent several years shaking down the Eastern Roman Empire, who had fairly unprofessional soldiers. Then UsefulNotes/AttilaTheHun got cocky and took on the West. The West had trained soldiers and every BarbarianTribe that Attila had ever wronged on their side. Not surprisingly, Rome won, and Attila died on his wedding night (not of a nosebleed as is commonly thought; his heavy drinking caused a hemorrhage in his esophagus, and killed him with a combination of choking on his own blood and shock) Now here's where Rome made a huge mistake: it let its Western army slack off, and discriminated heavily on the barbarians. Then, the barbarians all teamed up to form TheHorde and carried out what is still considered to be the greatest ever RapePillageAndBurn ever conducted. The raid was so devastating that not only were barbarians all over Europe able to reclaim their land while the Romans just stood there [[WatchingTroyBurn staring at the bonfire they used to call 'home']], but they actually destroyed 400 years worth of technology. DarkAgeEurope ensued.
** Rome did it for centuries: for their neighbouring Germans, serving in the Roman army was a way to get honour (as they knew that [[TrainingFromHell surviving the training meant you were a badass]]) and improving living conditions for themselves and their families upon discharge (they were allowed to settle inside the borders and got citizenship for themselves and their children). The difference was ''how'' it was done: for most of the time, the barbarians were split up and sent to serve inside units raised from fully Romanized populations, thus isolating potential troublemakers and expose them to Roman values until they adopted them. Sadly a series of civil wars and a major military campaign after emperor Valentinian III's death ended up depleting the Western army, with general Ricimer (commander in chief of the army and, by then, the real power behind the throne) opting to not have the veterans train new recruits raised from inside the empire but to have barbarian tribes replace the destroyed armies. As soon as that was done, Rome lost Spain, Africa and Gaul to the barbarians for good, and the empire in Italy would soon fall to the barbarians in the army deciding they're better off without an emperor.
* The elite Janissary forces of the old Ottoman Empire, later becoming a powerful military caste in their own right, began technically as BattleThralls, mainly from the then newly-conquered territories such as Greece and Bulgaria. The Ottomans would acquire suitable young boys for the Sultan from those territories specifically for this purpose, making it also a RealLife case of {{TykeBomb}}s.
** Well, ''almost'' a real life case of {{Tyke Bomb}}s. They were taken back to Istanbul and given extensive training (in reading, history and religion as well as fighting), so it would sometimes be years before they'd see actual battle.
* The Egyptian Mamluks had a similar origin as the Janissaries, though they eventually took over the country and ruled it until being conquered by said Ottomans.
* Christendom had its own equivalent to Mamluks and Janissaries, called Vavasours in France or Ministerialen in Germany. These were serfs who took on the duties of knights, becoming, in essence, unfree noblemen. They didn't have any land to leave their descendants, and their lords still controlled a lot of their private lives (like whom they could marry), but they still held the social esteem that came with knighthood. There were probably more Ministerialien in the Middle Aged Holy Roman Empire than free knights.
* The reason why the Mongols could show up in great numbers and plow through Muslim and Christian nations ([[Creator/MontyPython nobody expected the Mongol horde!]]) is because they made battle thralls out of every tribe they conquered along the way. And it was a long, ''long'' way.
* The British Empire was largely built on DefeatMeansFriendship, with the Scots, Sikhs and Gurkhas among their most elite troops.
* There was a type of fighting men in Muscovite Russia called ''boevye kholopy'', which literally translates to battle thralls. However, being a battle thrall was significantly more prestigious than being a plain old thrall, since Russian boyars typically equipped their thralls in good armor and used them to relay orders to common soldiers. A battle thrall was basically another instance of the boyar on the battlefield.