Technology & Combat Characteristics
Designated as the commander unit of the Earth Alliance's G Project due to its enhanced communication and analysis capabilities, the GAT-X303 Aegis Gundam also has heavy attack power as well as Phase Shift armor and can transform into a mobile armor (MA) due to its X300-series frame. In MA mode, it has two different sub modes, 'Cruise' and 'Attack'. When in 'MA Cruise Mode', the Aegis has higher speed and acceleration, while in 'MA Attack Mode', it can destroy an enemy ship/mobile suit with its "Scylla" 580mm Multi-phase Energy Cannon directly or grab onto them with its four limbs before destroying them using the cannon.
Other weapons of the Aegis included two head-mounted CIWS, a beam saber in each limb, a handheld beam rifle, and a shield. The Aegis has a large sensor unit at the top of its head and unlike most mobile suits, its main thrusters are located in the side binders on its waist. Due to the transformation system, its internal structure is more complex and it is for this reason that there are no mass production variants of the Aegis. The three different modes (MS Mode, MA Cruise Mode and MA Attack Mode) also means that the Aegis's pilot needs to have higher skills to be able to use the suit effectively.
History
One of the original five mobile suits created as part of the Atlantic Federation's G Project, the GAT-X303 Aegis Gundam rolled out on January 20, CE 71, together with the other units of the project. Stored in the colony Heliopolis, all but one of the G Project mobile suits were stolen by ZAFT on January 25. The Aegis was then piloted by ZAFT pilot Athrun Zala.
The Aegis was transported to Earth shortly after the Battle of Orbit on February 13 to pursue the Archangel. It was held at the Carpentaria Base in Australia until the Archangel passed through the Indian Ocean, where it was sent to rendezvous with the Vosgulov-class submarine Cousteau. Along with the GAT-X102 Duel Gundam, GAT-X103 Buster Gundam and GAT-X207 Blitz Gundam, the Aegis successfully intercepted the Archangel mid-ocean and forced the heavily damaged assault ship to lay over at Orb Union for repairs.
Its final battle occurred in mid April, while fighting Kira Yamato in the GAT-X105+AQM/E-X01 Aile Strike Gundam and Tolle Koenig in his FX-550 Skygrasper during the Battle of the Marshall Islands. There, Athrun destroyed the Skygrapser, killing Tolle, and fought a viscous battle with Kira. At the battle's climax, Athrun self-destructed the Aegis while grappling the Aile Strike, destroying the Aegis and heavily damaging the Aile Strike. He ejected beforehand and was found injured on the shore by Cagalli Yula Athha. Athrun returned to combat shortly after, piloting the ZGMF-X09A Justice Gundam.
The fragments of the destroyed Aegis eventually found their final, peaceful use as a playground for young children, on the same island where Athrun and Kira fought. Its shield was later found and sold at the black market auction for junk, which was listed by Lowe Guele and friends. The Aegis was used as the base unit for developing ZAFT's ZGMF-X11A Regenerate Gundam.
After the war, as part of the "Actaeon Project" MS development plan, another Aegis Gundam was manufactured and piloted by Phantom Pain pilot, Emilio Bloderick. The unit was later upgraded into the GAT-X303AA Rosso Aegis.
By May of C.E. 75, the head and most of the remaining wreckage of the destroyed Aegis Gundam still remained at the same island where Kira and Athrun fought.