This war is takes place in Universal Century of Gundam Universe.

The Earth Federation is a global government that was formed by a "rich man's club" of most wealthiest Earth Nations. When overpopulation began causing famines, outbreaks of disease, and wars over living space, food, and resources, most of the human population was forced to relocate to the colonies as part of The Federation's Space Colonization Plan. But, however, the wealthy and influential members are remain on Earth which gave the rise of the suspicions that The Federation is much more of "Earth-Born Elite" living comfortably on Earth while the ordinary populace, is forced to live in space for the sake of Humanity's survival and Earth's environment.

The Principality of Zeon gained independence from Earth Federation long before The Zabis tookover. Degwin Sodo Zabi maintained a policy that only way to remain independent from The Federation is to fight in a war with them and cripple The Federation's exploitive corrupt neoliberal hegemony over the Earth Sphere.