Several years before the Battle of Yavin, the planet of Anoat was gassed by the Galactic Empire. A group of dissidents were known to have been present on Anoat, but the Empire could not find their . Consequently, the Imperials decided to gas the whole planet, rendering Anoat toxic and poisonous, and forcing much of the population to flee their homeworld. It was Ubrik Adelhard, then a junior military advisor, who gave the order. Those who did not evacuate the planet ended up mutating, transforming into feral creatures known as Lurkers. The gassing of Anoat also taught the Alliance a valuable lesson, which was to avoid operating among civilians.
The Empire's official version was that Anoat had been poisoned and a few of its inhabitants "moderately damaged" by "a series of tragic industrial accidents."