Athrun Zala is the pilot of the GAT-X303 Aegis Gundam, ZGMF-X09A Justice, ZGMF-X23S Saviour, and ZGMF-X19A Infinite Justice, but while he is a soldier of ZAFT, he has a habit of defecting when the situation starts going against what he believes in.
Athrun Zala was born on October 29th, CE 55, in December CIty, and is the only son of Patrick Zala, a member of the PLANT Supreme Council. As a child, he was sent to a prep school on the moon where he met and became good friends with Kira Yamato. Athrun is particularly talented with mechanics and gifts a robot bird to Kira just before he leaves the school in CE 68. Patrick Zala arranged for Athrun to be engaged to Lacus Clyne, the daughter of Siegel Clyne, another Supreme Council member. Athrun does not protest this as Lacus is kind and good-natured, and gifts to her a robot Haro. (And when she expresses her delight, he responds by building her a veritable army of them.)
On February 14, CE 70, Athrun's mother is killed in what would later be dubbed the Bloody Valentine tragedy. Seven days later, he enrolls in the ZAFT military academy. There, he becomes good friends with Nicol Amarfi and Rusty Mackenzie. Upon graduation from the Academy, he and his friends are assigned to the Le Creuset special forces team along with Yzak Jule, Dearka Elsman, and Miguel Aiman. Fredrik Ades is the captain of their Nazca-class destroyer Vesalius, and their commander is Rau Le Creuset. The Le Creuset team is assigned the task of stealing the Earth Alliance's top secret mobile suits, the Gundams, from the Orb colony Heliopolis. On that mission, Athrun secures the GAT-X303 Aegis Gundam, but also spots his old friend Kira amongst the members of the Earth Alliance.