In the late U.C.0080s, the Mars-based Zeon Mars developed cooperative ties with Axis (later Neo Zeon), who was aiming to invade the Earth Sphere. Their direct collaboration, as seen with the dispatching of the Chester Jr. Fleet, also extended to technical matters such as mobile suit development. The latter was particularly beneficial, giving birth to mobile weapons that, though sharing the same technological lineage, were tailored to their respective tactical and operating environments, such as with the Reben Wolf and Fenris Wolf for Zeon Mars. In addition to these new models, Zeon Mars adopted the Zaku III (Type-R), the successor of the former Principality of Zeon’s Zaku, and the Dreissen (Dom III Zeon Mars version) as the successor to the Dom. Based on these trends, it was only natural that there’d be calls for a successor to the Gelgoog.

Axis had already developed the MS-14J ReGelgu as a modernized and upgraded version of the Gelgoog. Axis used the ReGelgu for training their new recruits. Along with the upgraded suits, newly manufactured units also saw operation, used specifically as commander’s units. On the other hand, Zeon Mars wasn’t particularly satisfied with the modifications to the older suit and elected to develop a new successor to the Gelgoog based on design data from the ReGelgu. The mobile suit developed and completed based on these circumstances is the MS-14J.zm Gelgoog III (Zeon Mars version).

The mobile suit was ranked primarily as a high-end suit for ace pilots and commanders, and a group of the suits that saw early completion was deployed primarily with the Chester Jr. Fleet, which had been sent to Earth to support Axis. Full-scale production was intended to follow, however, with the outbreak of the ReZeon Foundation War, production plans were delayed.

Despite the primary weapon for this suit being a beam rifle, the beam rifle for commanders’ suits was of a different type than the standard units as it had enhanced rapid-fire capabilities. The arm is equipped with a beam gun, while the head has built-in vulcan guns. The backpack adopts the same model as the ReGelgu, though the mounted missile pods on either side are larger, articulating type with larger rounds. As for hand-to-hand combat armaments, it is equipped with a beam lance, which can become a beam naginata by connecting the stock. The suit also carries a large shield.

Thus, the prominent characteristic of the Gelgoog III (Zeon Mars version) is its exceedingly Gelgoog-like overall silhouette, including armaments, which is said to embody the Zeon Mars ideology, which emphasizes the traditions of the former Principality of Zeon. Finally, there are many similarities with later Neo Zeon commander mobile suits both in appearance and mechanisms, which could be resultant of mobile suits left behind in the Earth Sphere used as a reference during development.