With the peace treaty, the space colonies unified with the Earth under the Earth Federation and became known as the United Government of Earth (UEE). However, the colonies' hatred of the Earth nations remained from the war's devastation. Under the pretext of peace, the anti-Earth forces were laying their groundwork to seize the universe again. The Earth nations came to realize they were being betrayed. That moment, a terrifying new enemy called "Vagan" that could not be beaten by a single nation's military forces appeared in the skies of Earth. They were swarming out from its base somewhere within the space colonies. The Earth was instantly filled with dismay and fear. The UEE was forced to merge the Earth nations' military forces, and the giant-robot "mobile suits" were born.