The year is 0079 of the Universal Century Calendar. It has been over half a century since man began colonizing space, and a number of colonies have been established since then. The cluster of colonies farthest from the earth, Side 3, declared themselves the Principality of Zeon, and began fighting a war for independence from the Earth Federation, the One Year War. In the first month of the war, the use of nuclear weapons, poisonous gasses, and colony drops, among other things, caused the loss of billions of lives, half the population on both sides.