The story is set in the same One Year War in UC 0079 as the first Mobile Suit Gundam anime series. It follows the battles between two ace pilots of the Principality of Zeon and the Earth Federation at the "Thunderbolt Sector," a shoal zone with numerous wrecks of space colonies and warships.
 
(Source: Anime News Network)

During the One Year War of U.C. 0079, the Earth Federation and Principality of Zeon engage in a fierce battle at the "Thunderbolt Sector", a shoal zone in the former Colony Side 4 "Moore". After successfully infiltrating Zeon's sniper field, ace Federation pilot and jazz enthusiast Io Fleming is given control of the latest Gundam prototype. 
(Source: Gundam Wikia)

In the Universal Century year 0079, the space colony known as Side 3 proclaims independence as the Principality of Zeon and declares war on the Earth Federation. One year later they are locked in a fierce battle for the Thunderbolt Sector, an area of space scarred by the wreckage of destroyed colonies.
 
(Source: VIZ Media)

Graham