At the beginning of Universal Century (U.C.0001), with the population reached 9 billion on Earth, people started to migrate from Earth to space colonies and the new history began.

      At U.C. 0058, Zeon Zum Daikun established Republic of Zeon in Side 3 and declared independence. At U.C. 0068, since the death of Zeon Zum Daikun, Degin Sodo Zabi became the leader and established Principality of Zeon. At this moment, the relationship between Earth Federation Government and Principality of Zeon became much worst. At U.C. 0079, Zeon declared the war against Federation Government and launched the space colonies as the weapons into Earth. The descension of space colonies seriously polluted the Earth and made many areas as deserts. Only at the first month of the war, both sides had totally lost over half of their population.

      At the beginning of the war, Zeon used Mobile Suit (M.S.), Zaku, as their main weapons, and beat the armies of Earth Federation Space Force (E.F.S.F.) again and again. Until Earth Fereration researched the remnants from Zaku II and started the Operation Victory that used the new M.S.s, Gundam, Guncannon, Guntank and the new space carrier, White Base in the battles, the war became an even match at this moment. This action also caused Zeon moves the battlefield back to space.

      During this war, rousing two excellent M.S. pilots: Amuro Ray, who came from Earth Federation Force. He accidentally controlled Gundam in Side 7 and fully used its function and power at the later of the war. He also progressively enlightened his New Type ability during the battles; Char Aznable, the famous Red Comet, who came from Zeon. Because of the revenge for his father, Zeon Zum Daikun, he became the captain of Zeon and started his revenge plan to his foe, the family of Zabi.

      At the end of U.C. 0079, Earth Federation Force used almost two third of the remainder armies to attack Zeon's last stronghold, A-Bau-Ku. This operation was called Operation Star One. At the final of this battle, Zeon had been defeated by Earth Federation Force and declared surrender, but Gundam and White Base were also destroyed at this battle. People named this cruel war that happened at almost a year of U.C. 0079 as the 'One Year War'.