BattleTech is a large franchise that rose out of the Humongous Mecha War Game created by FASA. Said game was based off a Real Robot reinterpretation of many classic mecha anime such as Super Dimension Fortress Macross and Fang of the Sun Dougram. It turned out to be a huge hit, leading to spinoffs such as a companion RPG called MechWarrior, a series of novels set in the shared universe which filled in the overarching story, multiple action and strategy video games, and even an animated series (notable for early usage of CGI).
Many of the designs of the original 'Mechs were taken straight from the animes noted above, with legal permission. However, due to a legal rights snafu with companies like Harmony Gold (owners of Robotech), several designs were forced to be declared the "Unseen" in 1996 and could not be visibly used in any media. This legal stalemate lasted until 2015, despite a change of ownership of the franchise (to Catalyst Game Labs). Catalyst finally redesigned the Unseen visually, so that they could be used without having to request permission.
The general story is that for centuries, humanity was united under the glory of the Star League, kept secure with humanity's greatest weapon, the bipedal armored robots known as BattleMechs. This golden age came to an end when an corrupt chancellor named Stefan Amaris took power for himself, fracturing the Star League. Amaris was eventually toppled by the great general Aleksandr Kerensky, only for him to leave known space with his forces in disgust when several warring galactic empires, known as the Successor States, formed and began to feud over who should reign over humanity. For centuries, these states waged horrific wars, sending technology and society further and further backwards. All the while, a secretive organization named ComStar hoarded what technology it could and destroyed what it could not, plotting to unify the newly christened Inner Sphere under its own banner. Most of the early works in the setting took place in the 31st century, as the Successor States continued to vie for territory.
These wars finally came to a halt when the descendants of the forces Kerensky had led out of the Inner Sphere returned. Rebranded as an alien society called the Clans, they invaded with the intent of capturing Terra, aka Earth, which was held at the time by ComStar. Once they learned of this, ComStar managed to stop the clans by way of a proxy battle for Terra on the planet Tukkayyid. Although they won, the political upheaval that followed led to ComStar splintering in two; one faction kept the original name, while the other became known as the Word of Blake (named after the founder of ComStar). A few years later, the Inner Sphere united again under the banner of the Star League, and attacked the Clans. The Clans fractured, with some joining the new Star League, others being driven back, and one of the Clans (Smoke Jaguar) being annihilated.
Shortly after that, war broke out again in what had been one of the major Successor States, the Federated Commonwealth. Eventually, the war led to the dissolution of the second Star League. Furious at this, the Word of Blake then broke out long-forbidden nuclear weapons, and proceeded to annihilate every planet they could, plunging humanity back into a new dark age. While there have been attempts to rebuild a new unified state since this, most of the Inner Sphere remains in chaos, engulfed in perpetual war between the remnants of both the Successor States and the Clans.
- Absent Aliens: A few novels (most notably Far Country) actually do have aliens. The rest? None. As for Far Country itself, the aliens in question live in a system that's only been accessed by humans twice, both in jumpship mishaps that leave the humans stranded there. So they exist, but they can't interact with the rest of the BattleTech universe.
- Anyone Can Die: The EU encompasses a time span of over a century; if combat, accidents, or assassinations fails to kill someone, old age will.
- Awesome Mc Coolname: Grayson Death Carlyle.
- Bullying a Dragon: Novel Close Quarters has the main character, Cassie, use a bolter on a battlemech to provoke it into chasing her. The metallic ping against the cockpit window is a direct insult to the 'MechWarrior's arrogance, which causes them to give chase. She runs through a few buildings before surprising the mech with an electrical attack to the knee joint. The electricity spot-welds the joint, and crashes the mech to on the ground. She repeats the same action later in the novel by attracting a mech into swampy terrain where it gets stuck and crashes onto the ground.
- Canon Immigrant: Some of the animated series' characters obtained this status. Adam Steiner is easily the most visible of them. Also of note are Vandervahn Chistu (Nicolai Malthus' superior) and Franklin Sakamoto. Chistu would briefly become one of the Falcon clan Kahns, ultimately dying at Vlad Ward's hands during the Refusal War. Sakamoto, on the other hand, would survive until the early stages of the Jihad in 3070. (Worth noting that Sakamoto was captured by the Black Dragon forces, with his ultimate fate apparently remaining unknown.)
- Changeling Fantasy: Subverted - Franklin Sakamoto renounced his claim to the throne.
- The Chessmaster: Subhash Indrahar, head of the Kuritas Secret Police for 60 years.
- Critical Existence Failure: The concept of Combat Loss Grouping; stastistically, mechs of a similar weight class will continue to fight for long periods of time before becoming combat ineffective all at once.
- Defeat Means Friendship: A common method for mercenary units looking to recruit people.
- Defector from Decadence: Trent of Clan Smoke Jaguar. Having been a victim of politics several times (his sibmate changes the official report of the battle of Tukayyid, and then manages to steal his spot on the Trial of Bloodright), with the help of his bondsman, he manages to escape his Clan, goes to Com Star and gives them the Exodus Road, the path to the Clan homeworld.
- Dysfunction Junction: The Seventeenth Recon Regiment, aka "Camacho's Caballeros". Their top scout is a recovering sociopath, one of their best captains is a repeated rape victim, another is clinically insane (and proud of it), and their commander is grieving his deceased daughter while his surviving son suffers from "Well Done, Son!" Guy.
- Everything's Louder with Bagpipes: The Northwind Highlanders have their bagpipe band play the loudest song possible onto Clan Smoke Jaguar radio frequencies to jam up the Clan's communications, forcing the Clanners to use more troublesome line of sight based communications.
- Faking the Dead: Galen Cox. It's part of an elaborate scheme to expose Katherine Steiner-Davion's duplicity.
- Good Is Not Nice: Again, too many to list. Gray-and-Gray Morality is a big part of life in the Inner Sphere.
- Happily Married: Hanse might have married Melissa for political reasons, they did make it work and love each other.
- HeelFace Revolving Door: Tormano Liao. Basically, he's on whatever side is against the Capellan Confederation at the moment.
- Honor Before Reason:
- Common with the Clan warriors and the older-line Draconis Combine warriors and nobility.
- Also, this is why Myndo Waterly thinks that Anastasius Focht won't just shoot her. She's wrong.
- Impossibly Graceful Giant: The first BattleTech novels had mechs doing rolls, going prone, and doing other silly maneuvers. Later novels makes them much more tank-y like in the boardgame.
- Kill It with Fire: One of the most effective anti-Mech weapons an infantryman can carry is the Inferno rocket, which is loaded with a napalm substitute that overheats the Mech and cooks the pilot inside. As a result, fear of death by fire is common among MechWarriors.
- Killed Off for Real: Takashi Kurita, Subhash Indrahar, Omi Kurita
- Manipulative Bitch: Katherine "Katrina" Steiner-Davion. For example, she seizes control of an entire interstellar nation just by rigging their popularity polls.
- Memetic Badass: In-universe, Kai Allard-Liao. To the point where Clan commanders sending fifty Elementals to hunt him down (while he's injured, without a 'Mech, and on the run behind enemy lines), is considered a "fair fight".
- Names to Run Away from Really Fast: Ninyu Kerai. Subhash Indrahar apparently used to be one before old age caught up with him.
- Nice Job Fixing It, Villain!: In Mercenary's Star, a Kurita assassination attempt on a Lyran ambassador is exactly what convinces said ambassador to send reinforcements to the Gray Death Legion.
- No Celebrities Were Harmed: Johnny Tchang is a straight expy of both Bruce Lee and Jackie Chan. One of his films is even called Exit The Dragon.
- The Plan: Just like being a badass seems to be a requirement for surviving warfare, mastering gambits seems to be required for successfully holding any kind of political power.
- Royally Screwed Up: Both the Liaos until Sun-Tzu and the Kuritas until Theodore are this.
- Rule of Cool: The actual rules of the original game frequently get tossed aside in favor of this. Hey, whatever works...
- Some of these incidents, such as an Atlas throwing the much smaller Locust around like a rag doll (often alluded to in fluff) were finally canonized as game rules to get players to stop complaining about not being able to do what was in the fiction.
- Sometimes averted; the climatic action sequence of Grave Covenant and most of the 'Mech combat sequences that don't involve Morgan Kell or Yorinaga Kurita in the Warrior Triology appear to have been actually gamed out under the tabletop rules. The Grave Covenant scene with Victor's Daishi and Renny Sanderlin's Penetrator is even in one of the scenario books.
- applies within the tabletop game: the reason why these giant, 31st century weapons have ranges in only hundreds of meters is Rule of Cool. Otherwise maneuver would have been pointless within the game.
- Sir Swearsalot: Clan pilots. Expect Clan character's dialogue to be about 20% cussing (in the Clan's vocabulary, which means loads and loads of "FREEBIRTH" and "STRAVAG" being yelled)
- Star-Crossed Lovers: Justin Allard and Candace Liao (who end up Happily Married and produced the aforementioned Memetic Badass Kai), and later Victor Steiner-Davion and Omi Kurita (which doesn't end nearly as well).
- Stockholm Syndrome: POWs of the Clans start out as bondsmen, but are given the chance to regain their warrior status if they pass a Trial by Combat, upon which they become a fully fledged member of the capturing Clan. The most extreme example would be Phelan Kell a captured Inner Sphere mercenary (the Clans viewed these as the lowest form of scum) who not only earned his own bloodname (and by that, I mean he had a bloodname named after him), but would go on to become the leader an entire Clan subfaction.
- The Reveal: The history of the Clans, and the nature of Wolf's Dragoons.
- Unresolved Sexual Tension: Kai Allard-Liao and Deirdre Lear. That would be until they got married. Or possibly earlier.
- Their son, David Lear, was born shortly after they separated on Twycross, long before they got married. Kai was unaware he had a son for a while. So definitely earlier.
- Also a very "star-crossed lovers" example in Victor Steiner-Davion and Omi Kurita. They fall in love with each other at just about first sight when meeting on Outreach, but he's the heir to the Federated Commonwealth and she's the daughter of the Coordinator of the Draconis Combine and they're both too conscientious to just shirk their responsibilities in the name of romance... They do get together in the end, although eventually an assassin sees to it that it doesn't last forever.