Dan Simmons' 'Hyperion Cantos' has the Hegemony, a human interstellar government, constantly expanding through farcaster portals. Their expansion brings them into conflict with the Ousters, humans who rejected Hegemony rule and adapted to life in space.
To the Hegemony, the Ousters are barbarians. To the Ousters, the Hegemony's rigid, ecosystem-destroying colonization is the true invasion. Later, with the TechnoCore and the Shrike, humanity's entire history is reframed as a manipulated, invasive growth across the galaxy, a cancer that more advanced entities are trying to control or eradicate.