They only invaded because they were fleeing from a Doomed Hometown
Our heroes' hometown is invaded or simply attacked suddenly by enemies, so they fight them off. Later, they find out the invaders weren't actually invading, but actually fleeing from something much worse than them. Can result in an Enemy Mine in order to deal with the bigger threat. Alternatively, the invader's home may have been or about to be lost to a disaster and the heroes may help them in restoring their home, finding them a new one, or prepare for the disaster when it reaches their home. May result in the third variation of Planet Looters.
- How to Train Your Dragon: this turns out to be the reason dragons raid villages.
- The Honored Matres in the Dune universe (who appear in the last two Frank Herbert novels of the series, Heretics of Dune and Chapterhouse: Dune) are aggressors who attack many worlds and wreak havok in the old Empire--but it is stated they are fleeing an even more powerful and terrible mysterious enemy.
- Crayak, the Bigger Bad of Animorphs, is said to be fleeing something even worse than him.
- The Abominor, a villainous robot species that turns up in a couple Star Wars Expanded Universe novels (along with their enemies, the much nicer Silentium), is known to be from another galaxy and fled from an organic species, heavily implied to have been the Yuuzhan Vong.
- The Canim of the Codex Alera are eventually shown to be this, and the protagonists actually go to Canea and see what chased them away.
- The Insects From Shaggai (AKA Shan) in Ramsey Campbell's Cthulhu Mythos stories. When their home planet was destroyed by a Mythos abomination, some of them fled to a succession of other planets, finally ending up on Earth. They're still pretty evil by human standards.
- Several races in the revived Doctor Who tried to colonise Earth because their home worlds were destroyed by some greater threat. To wit:
- In series 1, the Nestene consciousness in "Rose" and the Gelth in "The Unquiet Dead" were fleeing the great Time War.
- In series 4, the Pyroviles in "The Fires of Pompeii" had their planet taken by the Daleks as revealed in the series finale.
- In series 5, the fish-aliens in "The Vampires of Venice" fled from the Silence through the cracks in the universe.
- In Defiance, the Votans arrive in space arks after fleeing the destruction of their solar system when its sun went nova.
- In Babylon 5, the Dilgar began conquering other solar systems and doing unspeakable things to the inhabitants when they discovered their sun was about to go nova. The Earth Alliance drove them back and the nova wiped them out.
- It is implied by some Warhammer 40,000 fluff that something even worse than the tyranids is chasing them into the Milky Way.
- Dungeons & Dragons 1st Edition supplement Oriental Adventures: in the section on randomly rolling up yearly events, one example of a Major Incursion was a barbarian horde that had been driven from its homeland.
- As the Toa Metru journeyed through the Maze of Shadows, they were frequently attacked by Rahi running in their direction. After some battle they realize these Rahi were fleeing something away from where they were heading.
- The Rock Tribe from the north initially partake in the Glatorian system before straight up invading other tribes for resources. It turns out they were only doing this because the Baterra drove them out of their old home and killed a significant portion of the tribe.
- The orcs in Sacred aren't launching an invasion of the human kingdoms, they've been displaced from their homeland by the arrival of a horde of undead.
- Warcraft III: The night elves of Northern Kalimdor initially take a dim view of the orcs and humans who have arrived on their continent and despoiled their forests, even when it becomes clear that they are refugees fleeing from The Scourge and The Burning Legion. But they eventually join an Enemy Mine alliance once it becomes clear that The Legion poses a much bigger threat to them and their beloved forests than the refugees.
- The Tasen from Iji bombarded Earth to make place for them running away from Komato that want to annihilate them completely.
- In Ultima VI, the Gargoyles, who are presented as demonic invaders at first, are eventually revealed to be fleeing to Britannia from the collapse of their homeworld, inadvertently caused by the Avatar's own actions in the two previous games.
- The Vortigaunts and other Nihilanth's soldiers in the first Half-Life. Turns out, they were fleeing the Combine.
- In the backstory for Halo 4, we find out that the forerunners have had a history of conflict with humans, leading to the Didact's current hatred of them. In reality, humanity was just trying to wipe out the flood, and fled from infected planets into inhabited ones
- In Gears of War, the Locust Horde only emerged from their underground lairs and fought humanity because their homes were overrun by another, even more dangerous entity.
- An episode of The Legend of Tarzan had the gorillas' home invaded by the rhinos. It turns out that they've been displaced by a trading post. The owner of the trading post gives Tarzan a line of credit for some dynamite, which he uses to blast out a new home for the rhinos to live in.
- The Goths and Vandals who invaded Roman territory were fleeing from Attila the Hun.
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