March 1992. Probably the most interesting change the ROBOTECH storyline makes to the plots of the three Japanese anime series from which it's derived is that in ROBOTECH, the Invid, the snail-like alien race that conquers the Earth at the beginning of the NEW GENERATION/GENESIS CLIMBER MOSPEADA storyline, are a colonized people, interstellar refugees. As explained in the Jack McKinney novels and later dramatized in the six-issue miniseries ROBOTECH GENESIS: THE LEGEND OF ZOR, based on Carl Macek's story notes, centuries ago, the Tirolian scientist and explorer Zor visited the Invid homeworld, Optera, and discovered that the Invid "Flower of Life" could be used as the basis of a potent form of bio-energy he called Protoculture. Zor stole the secrets of the Flower and took them back to Tirol, where Protoculture soon sparked a technological revolution that created space fold travel, reflex weaponry, and bioengineering. The lords of Tirol, calling themselves the Robotech Masters, used this power to annex their neighbors, and created the giant Zentraedi to police their new empire. The Masters then ordered the Zentraedi to defoliate Optera to monopolize their control of the Flower. The surviving Invid split into two factions: one, led by the Regent, fixated on vengeance against Zor and the Masters, and the other, led by the Regiss (or Regis), determined to find a new home and a new evolutionary form that would enable their survival. The Invid later killed Zor, but not before he sent the last Protoculture factory to Earth (as shown in the 1986 ROBOTECH graphic novel), hoping in vain to put it beyond the reach of the Masters.
When Zor Prime, a clone of the original Zor, destroys that factory at the end of the ROBOTECH MASTERS/SOUTHERN CROSS segment of ROBOTECH, it effectively seeds the Earth with the Flower of Life and draws the attention of the Regiss, who invades in hopes of finally reclaiming what had been stolen from her. (This isn't the case in the original MOSPEADA storyline, where the Inbit simply invade Earth because it seems like a habitable spot for their eugenics project.)
This is a clever amalgamation of ideas from the original shows, and it gives ROBOTECH a very different perspective on colonialism than the original series. MACROSS says explicitly that the devastation of the Zentraedi holocaust makes the colonization of other worlds a moral imperative for the human survivors; the original SOUTHERN CROSS storyline is about defending a human colony world (established after a nuclear war devastated Earth) against the return of that world's weird and malevolent original inhabitants; and MOSPEADA ultimately suggests that the Regess has been a more-or-less benevolent, religiously motivated colonizer who leaves the Earth better than she found it. The ending of ROBOTECH is a series of moral reversals: The Invid Regiss has gone from refugee to conqueror, doing to the humans what the Masters and the Zentraedi did to her, but at the same time, the human survivors of the war with the Zentraedi have in effect become the new Robotech Masters (something the Regiss says pretty explicitly in her final monologue), prepared to replicate the devastation of Optera and the Zentraedi holocaust to keep the Regiss from winning. Her ultimate departure, which also destroys the attacking REF fleet, is driven by shame, and a desire for a very literal kind of restorative justice that seeks to redress the humans' sins as well as her own, which makes for a morally complex and bittersweet finale for the saga (the misbegotten SHADOW CHRONICLES notwithstanding).
