Although their continuation was permitted following the One Year War, the Republic of Zeon was nothing more than a dominion of the Federation Forces and as such, possession and development of weapons was considerably restricted. The Republic never took responsibility, putting most of the blame of the war on the Zabi family, yet the nation bearing the name of “Zeon” had the likelihood of being the unifying force for the Spacenoids and the Federation government had their misgivings about that.

However, due to the uncertainty surrounding the ceasefire agreement, remnants of the Principality forces questioned the legitimacy of the Republic of Zeon. Many Spacenoids also regarded the Republic as a puppet regime of the Federation and establishing the Republic’s government seemed to have been less welcomed. Nevertheless, the Republic government never attracted the attention of the Federation Forces due to the lack of contact with Principality remnants and it was fortunate that although the prosperity it once had was lost, it survived.

With that, the Republic was reluctant to augment its own military forces and the ships deployed for monitoring and self-defense of territorial space were upgraded version of the craft used by the former Principality forces. Even with this level of equipment, it was necessary and sufficient for the Republic government. On the contrary, further updates would attenuate the national strength and furthermore draw suspicion from the Federation Forces.

As a result of the severe restrictions imposed on mobile suits as well as on construction and possession of ships, the mobile suits loaded on the Modified Musai were not the most advanced units and it would seem that only second-best suits were approved by the Federation Forces (represented by the Hi-Zacks circa the mid-0080s).

The Musai Modified is an upgrade of the Musai-class utilized by the former Principality of Zeon forces. Whereas the armed forces of the 0080s deployed newer ships which introduced state of the art technology and equipment, this was dismal for the Republic. However, this level of equipment was sufficient for a nation that was permitted to continue, overlooked by the Federation government.

The Musai Modified became the main ship for the Republic government due to the large number of original Musai’s constructed. However, the upgrades were limited to enhancing the output of the thermonuclear reactor and modifying the shape of parts, but otherwise the basic structure hardly changed from the Musai-class. This relates to the financial situation and foreign policy of the Republic government, but the fact remains that the basic design of the Musai-class was exceptionally strong.

The weapons layout of the Musai Modified remains the same as the original but there were improvements made in terms of functions for the firepower and firing range. There are also a few additional armaments.

Sometime in U.C.0094, ships are seen at the resource satellite of Palau, utilized by the Sleeves. In the events of the OVA, one of the ships docked at the satellite is destroyed during Operation Billiard in the ensuing battle. In the events of the novel, the Musai Modified (called Advance Musai) also serve as escort ships of the 45th Training Fleet under the Republic of Zeon. In May U.C.0096, two ships the Gulltoppr and Dromi leave their flagship Birfrost behind during their long navigational training and head off to capture the Nahal Argama. However, they are ultimately destroyed by the hyper mega particle cannon near the L1 Junction.

Heat sinks have been added to the side of the engine nacelle to improve efficiency. Furthermore, the direction of the slit in the front has been changed from a horizontal to vertical direction which may also be related to efficiency.

The basic structure and position of the bridge is based on the Musai-class but the shape has more of a sharper angle. In addition, two antennas have been added to the top of the bridge to enhance communication functions.

The main weapons of the ship are the twin-barrel mega particle cannons which are used for anti-ship bombardment. Since there are three rows arranged vertically, it’s possible for concentrated fire towards ships in front. The shape of the turrets has been completely remodeled. The single-barrel secondary cannons are small caliber cannons that are newly added weaponry on the ship. Emphasis was placed on rapid-fire properties rather than firepower itself and they’re used for anti-air defense.

Launch tubes fire missiles from the front of the bow. Their speed may be slow, but they pack a punch and are used in attacks on colonies and enemy bases.

The Komusai atmosphere reentry capsule is mounted below the bow. It is unknown how the Komusai were developed from the Musai as there is no operational records.