Following the establishment of space colonies, tensions between their inhabitants and the Earth Federation gradually increased. The Republic of Zeon pushed for independence, but the Federation applied sanctions to the colony, fearing it would disrupt peace. After a change of leadership, Republic of Zeon became the Principality of Zeon, a despotic, militarized state with a visible intention to achieve independence by any means. Soon the conflict evolved into the deadliest event humanity has ever known - the One Year War.