The Oasis Government is the dominant authority within the Great Kanto Desert that had arisen presumably thousands of years after an event known as the Dark Ages in the area that had once been Japan before the event occured. It is assumed that the government had been split into several different parts each one having control over a directional region such as East, West, North and South as mentioned in the anime and manga, these may also just be outposts for those regions of the Desert to maintain order and providing the bare minimum for the citizens. It was later revealed that the Oasis Government operates out of a massive subterranean structure to the point that they only use half of the space and by the time of Episode 19 the remaining half has yet to be explored.