The Ancient Roman legions made up one of the most Badass Armies known to history. However, as powerful, disciplined, and successful as they were, they weren't invincible; on multiple occasions, they were defeated in battle, and sometimes an entire legion was destroyed in a single dramatic battle, or else simply disappeared while on campaign with none returning to tell what happened.
Of course, people are free to speculate on what happened to those legionaries who went missing in action. That is where this trope comes into play.
There are usually two distinct ways this trope plays out:
- The story follows another Roman legion which has been sent to find out what happened to the lost legion and (if possible) recover its Eagle Standards. This one tends to appear more often in Historical Fiction.
- The story follows the lost legion itself and / or its descendants (assuming it leaves any behind). While also somewhat common in Historical Fiction, the idea of a Roman legion displaced in space, time, or dimension has been used so often in Science Fiction and Fantasy as to be regarded as cliche. Does not always end happily.
Many stories that use this plot are inspired by any of three particular cases of actual "lost legions" in Roman history: Crassus' defeat at the Battle of Carrhae, the destruction of three legions in the Teutoberg Forest, or the mysterious case of the Ninth Legion.
- Alix #6 : Les légions perdues ("The Lost Legions") occurs during the war between Julius Caesar and Pompey
- The Sandman issue "Exiles" concerns people becoming trapped in "soft places" where the world is not quite real; one such group is a lost Legion having suffered this fate.
- In another one of Neil Gaiman's works, Neverwhere, the character Door encounters a Roman legion in the London Underground in a pocket of misplaced time. She says she thinks it was the Nineteenth - the legion usually thought to have been lost in Britain is the Ninth.
- Originally, the X-Men and New Mutants member Magma came from a lost Roman colony in the Amazon rain forest, but this was later retconned as a magical deception. And later retconned back. Maybe.
- A Savage Sword of Conan story had Conan trying to figure out what happened to a missing Aquilonian legion (and the large amount of gold they had with them). Long story short, they killed each other out of greed. Not strictly an example of this trope, but Aquilonians are basically Hyborian Romans.
- In Ranks of Bronze, the defeated and enslaved remnants of Crassus' legions are bought by an alien guild to fight wars against low-tech planets on their behalf due to a sort of twisted Prime Directive that requires them to use equivalent-tech weapons against undeveloped planets.
- The Alerans from Codex Alera are descended from a lost Roman legion that fell into Another Dimension where a lot of other creatures fell, which include but are not limited to saber-tooth tigers, 8ft tall wolfmen, empathic yetis, magical spirits, and basically the Zerg. The series actually started as part of a bet between Jim Butcher and an unnamed person on an internet chat board back in the late 90s, early 2000s. Butcher felt a good author can turn even the worst idea into a story, while the fan claimed some ideas are just unwritable. To prove a point, Butcher let the person choose two horrible cliches that he (Butcher) would write a story based on. The fan chose the Lost Roman Legion...crossed with Pokémon. The rest is history.
- The Videssos Cycle features one of these as the driving force in the plot, as evidenced by the title of the first novel, The Misplaced Legion. Bonus points for including a misplaced Gaul prisoner along with the legion.
- The Eagle of the Ninth deals with the aforementioned Ninth Legion.
- Eagle of the East by L. S. Lawrence follows the legion from the Battle of Carrhae.
- The fate of the Ninth Legion is a plot point in one of David Gemmell's Ghost King. This one also connects the lost legion with King Arthur.
- Andre Norton:
- From the prologue of Star Rangers:
There is an old legend concerning a Roman Emperor, who, to show his power, singled out the Tribune of a loyal legion and commanded that he march his men across Asia to the end of the world. And so a thousand men vanished into the hinterland of the largest continent, to be swallowed up forever. On some unknown battlefield the last handful of survivors must have formed a square which was overwhelmed by a barbarian charge. And their eagle may have stood lonely and tarnished in a horsehide tent for a generation thereafter. But it may be guessed, by those who know of the pride of these men in their corps and tradition, that they did march east as long as one still remained on his feet.
- Norton later co-authored Empire of the Eagle, a fantasy involving enslaved men of Crassus' army who're displaced into another universe after being given to a Chinese emissary.
- From the prologue of Star Rangers:
- H. Warner Munn wrote a 1980 novel titled The Lost Legion, which he specifically said in the foreword was partly inspired by the Andre Norton prologue above. Caligula ordered the legion east, ostensibly to search for possible descendants of survivors from Crassus' legions. In the end, as Norton described, "the last handful of survivors" was overwhelmed by proto-Mongols. But men from a Chinese garrison rescued the eagle ... and gave it a place of honor in their temple with the eagles their ancestors had brought east — so, in a sense, the legion did accomplish its assigned mission.
- In a story in one of the Man-Kzin Wars books, it turns out a legion from Britain was kidnapped by the last free Jotok to serve as footsoldiers against the Kzin. By the time of the story (only a few generations for them due to Time Dilation), the free Jotok have died out, but the Romans are still holding out, and are conveniently rescued by modern humans just when said modern humans were themselves warring against the Kzin. They're promised a planet of their own once the war ends.
- In Percy Jackson and the Olympians, Frank Zhang is descended from Roman Legionaries who reached China and established themselves in a city called 'Li Jien'. More specifically, the Romans he's descended from were the ones captured at the Battle of Carrhae, who were then put to work by the Parthians...who were then attacked from the other direction by the Chinese.
- The entire Roman demigod camp is the Twelfth Legion Fulminata, directed by Jupiter to continue Rome's legacy even after its fall.
- William Forstchen's The Lost Regiment series focuses on a variation of the theme: a Union regiment from the American Civil War that travels through a portal to an alien world, where they encounter both an alien race that feeds on humans and multiple societies set up by previous groups of humans that were stranded there. Among their eventual allies are the descendants of a lost Roman legion.
- The Forgotten Legion by Ben Kane uses the defeat at Carrhae to take the protagonists into Parthia.
- The Last Legion by Valerio Manfredi, adapted into a film of the same name (see above), involves the Ninth Legion.
- Lovecraft's short story The Very old folk combines this trope with his usual themes in the form of an Apocalyptic Log and All Just a Dream.
And then I waked. It was the most vivid dream in years, drawing upon wells of the subconscious long untouched and forgotten. Of the fate of that cohort no record exists, but the town at least was saved—for encyclopædias tell of the survival of Pompelo to this day, under the modern Spanish name of Pompelona
- Clive Cussler's Dirk Pitt finds the remains of a lost Roman legion. In Texas ("Treasure").
- Doc Savage:
- In Land of Long Juju, the But Not Too Black nature of the royal family of an African nation is explained by them being the descendents of a lost Roman legion that invaded central Africa and interbred with the local tribes.
- In The Forgotten Realm, the Ninth Hispana founded a city called Novum Eboracum ("New York") in the African Congo, which survived until at least the 1930s.
- In one of the Sister Fidelma stories (set in the seventh century) by Peter Tremayne, a distant relative of one of the officers who vanished with Legio IX Hispana asks Fidelma to help him find out what happened to the legion and recover the Eagle Standards. This man produces an apparent historical document which leads him and Fidelma to Canterbury where they find some eagle standards and further documents claiming the lost officer to whom the man is related died a hero. Unfortunately for him, Fidelma is a professional investigator and easily proves that the documents and eagles are very poorly made modern forgeries.
- Doctor Who: In "The Eaters of Light", the Doctor and Bill go to find out what really happened to the Legio IX. It turns out that most of the Legion was slaughtered by an alien creature that came out of a time rift, and the survivors volunteered to go through the rift and prevent the rest of the aliens coming through and devastating Earth.
- In Hero Games' Lands of Mystery, one of the groups populating the world of Zorandar were descended from a Roman legion that accidentally marched through a gate from our Earth.
- Homaged in Warhammer 40,000, where two of the twenty original Space Marine Legions have been struck from all records, "order origination unknown." The designers admitted they liked the idea of legions being declared in damnatio memoriae, and also wanted to give fans some Canon Fodder to play with.
- King Arthur: The Role-Playing Wargame: In the prologue of the second game (that comes with pre-ordering or can be purchased as Downloadable Content), Roman commander Sulla travels to the netherworld and recruits the lost 9th legion albeit in a Power at a Price fashon: His mortal soldiers must be possessed in order for them to fight for him. You get forced to do so even if you say no repeatedly. In the main campaign, you have to fight against these "undying" units; until you seal the three gateways to the netherworld, the entire armies you kill of them just keep re-appearing on the campaign map.
- One of the featured historical battles in Rome: Total War is the Battle of the Teutoburg Forest, where the player-controlled Roman legion has to escape a barbarian trap, or be slaughtered.
- The sequel also includes a portrayal of the Teutoburg ambush.
- In The Elder Scrolls series, the Imperial Legion is heavily based on the Roman Legions. The 10th Legion is said to have been completely wiped out during Emperor Uriel Septim V's failed invasion of Akavir, along with Uriel V himself. Of course, considering they were covering the retreat of the rest of the Imperial forces, no one really knows for sure.
- The Legion IX Hispana themselves show up as an SCP. Interestingly, conversations between one of the officers and Foundation personnel masquerading as Roman legionnaries indicate that they disappeared when the entire legion somehow had gained the ability to uncontrollably teleport to wherever Rome was fighting, which explains the evidence of them showing up in other Roman battlefields. This new ability, however, severely disorients them and makes their memories very confused.
- The Battle of the Teutoburg Forest in AD 9 was a catastrophic defeat for Rome; the legions XVII, XVIII, and XIX being completely annihilated over the course of the three day engagement. Eighteen thousand legionnaires, plus an equivalent number of auxiliary formations, totaling one-tenth of the entire field army were permanently lost beyond recovery. The Romans themselves were thunderstruck by the disaster and the crisis nearly turned to general panic. The Emperor Augustus saw the ruin of his ambition to conquer and assimilate middle Europe and later, on his deathbed, he advised his successor not to expand the empire for any reason. It was such an ignominious defeat that no Roman legions were ever named the 17th, 18th or 19th after that.
- The Legio IX Hispana (9th Spanish Legion) of the Roman army, a unit with a fairly well-documented history from the 1st century BC onward and which was stationed in Britain since the conquest of that province, disappears from historical sources around 120 AD. This has led to the assumption (first popularized by Theodor Mommsen) that the legion was completely destroyed in a catastrophic defeat against British Picti not long after 108 AD. This scenario was then further developed by Rosemary Sutcliff's historical novel The Eagle of the Ninth (1954), which posits that the legion was wiped out during an operation north of Hadrian's Wall, and revolves around a young Roman officer trying to uncover the circumstances of the legion's disappearance. Sutcliff's book has fostered the misconception that the "disappearance of the 9th Legion" was a real disappearance, rather than a "disappearance from the historical sources"; but while it is likely that the apparent disbandment of the Legio IX Hispana was preceded by a severe defeat, there is no reason to believe that the fate of the legion was a mystery in its own time. Furthermore, traces of the Legio IX Hispana from c. 120 AD have been found in Nijmegen in the Netherlands in the 1990s, which goes to show the hypothetical defeat did not even necessarily take place in Britain. Finally, the construction of Hadrian's Wall started in 122 AD, so the idea of anyone going or disappearing "north of Hadrian's Wall" before that date is an anachronism.
- In the 1940s, American sinologist Homer H. Dubs elaborated the hypothesis that the Chinese village of Liqian was founded by Roman survivors of the Battle of Carrhae, taken east by the Parthians and then captured again by the Chinese at the Battle of Zhizhi in modern Kazakhstan, some two decades later. This idea rested on supposed Caucasian features of the inhabitants, the similarity between the name Liqian and the word Legion, and a mention in a Chinese chronicle of the capture of enemy soldiers in a "fish scale-like formation" at Zhizhi, that Dubs interpreted as a description of the Roman Testudo. Dubs' hypothesis has not been confirmed by either archaeology or genetics studies done in Liqian.