Since the Izumo-class was the basis for the Archangel-class assault ship, the weaponry of both classes are nearly the same, although all in all the Izumo-class carries less weaponry than the Archangel-class. The armament features positron blaster cannons, beam guns, CIWS and several missile launchers.
- The strongest weapon of the Izumo-class are two dual "Lohengrin" positron blaster cannons, which are retractable and mounted in the sides of the rear engine sections. Unlike the ones equipped on both the Archangel-class assault ships; Archangel and Dominion- the cannons can fire either a single positron blast for an instantaneous destruction against entire mobile weapon groups or split the beams into four; enough to punch right through enemy warships like the Nazca-class.
- High-energy Beam Gun
- The only other beam weapons carried by ships of the Izumo-class are two "Gottfried" Mk 71 225cm Dual High-energy Beam Guns, which are mounted on rotating hardpoints that allow them to cover a wide firing angle. In the same manner as Archangel-class, the Gottfrieds are also retractable.
- The only shell firing weapons on the ship are 20 "Igelstellung" 75mm Automatic Multi-barrel CIWS guns, used to shoot down incoming missiles or Mobile Weapons. As a point defense weapon, the Igelstellungs are mounted on hardpoints spread over the hull of the ship so as to cover a maximum number of approaches.
- Missile Launchers
- Besides its energy guns and shell-firing weapons, the Izumo-class is also equipped with a large number of missile launchers, which are divided into surface-to-ship and surface-to-air types.
As with the armament, the interior design of the Izumo-class is very similar to the interior of the Archangel-class. The Izumo-class nevertheless differs from the Archangel class in several points, such as with its modular design.
A unique feature of the Izumo-class is its ability to split itself apart into five smaller modules. This allows the Izumo-class to jettison the forward and rear modules containing most of the weaponry, and replace them with a separate forward module for atmospheric entry and launches back into space. Once the core module descends to the surface, the armament modules remain in orbit to be recovered upon the ship's return. Due to its lower mass compared to the whole ship, the single module can easily be sent up into space using a Mass Driver, making transport between planet and space much more cost-efficient.
The Izumo-class battleships are powerful warships of the Orb Union which were created at an unknown point of time before CE 71. When the Earth Alliance started their G Project, they also planned to create a mobile suit carrier ship, for which the Izumo-class became the basis. The result was the Archangel-class. Over time, at least four Izumo-class ships were built.
The original ship of the Izumo-class and namesake of the class belongs to Orb's Sahaku family. At first the ship is used by Rondo Gina Sahaku as its base of operations. Gina planned to strengthen Orb's position by playing the Earth Alliance and ZAFT against each other. He was however eventually killed by Gai Murakumo. Afterwards Gina's twin sister Rondo Mina Sahaku took control of the Izumo and continued her brother's plans, although not with such extreme measures as her brother.
This ship belongs to the Athha family and was used in CE 71 by Cagalli Yula Athha and Ledonir Kisaka to escape the invasion of Orb by the Earth Alliance. The ship, together with the Archangel and Eternal, formed the Three Ships Alliance, a small group which planned to end the First Alliance-PLANT War. The Kusanagi took part in the battles at the Mendel colony as wells as destroying the Vesalius, and the final battle of the war, in which it attempted to destroy the GENESIS super weapon.
During the Second Alliance-PLANT War, the Kusanagi, together with two other Izumo-class ships, departs from Copernicus city on the moon to join up with the other ships of the former Three Ships Alliance as well as renegade units of the Earth Alliance and ZAFT (The Terminal Fleet), to stop ZAFT forces, who had just fired the Requiem at the Earth Alliance's Arzachel lunar base. The Kusanagi fired its Lohengrins at the Requiem only to have it blocked by multiple Positron Reflector shields deployed over the mouth of the moon-based superweapon. Eventually the Kusanagi survived the final battle around the Mobile Space Fortress Messiah despite the fact that it was fired upon twice by the Neo-GENESIS laser system aboard the space fortress.
As seen during the Second Alliance-PLANT War, at least two more ships of the Izumo-class are seen, which are known as the Susanoo and Tsukyomi. The two ships, together with the Kusanagi, were used to attack the Requiem cannon. However, their Lohengrin cannons proved ineffective against the new positron reflector around the Requiem. All Izumo-class, along with the Archangel and the Eternal were able to avoid the blast from Neo-GENESIS.
- The name "Izumo" comes from a region of Japan which is believed to be the place where the Storm god Susanowo descended to Earth when banished from heaven.
- Kusanagi is the second name of the sword, the Ame-no-Murakumo, which Susanowo pulled from the tail of the slain Yamato no Orochi and presented to his sister, the Sun goddess Amaterasu, as a reconciliation gift. Kusanagi is the sword of the Japanese Imperial regalia.
- Susanowo, as mentioned above, is the Shinto god of the sea and storms.
- Tsukyomi, also spelled Tsukuyomi, is the god of the moon in Shinto mythology.
- Kusanagi never appeared in any Super Robot Wars series. It is usually replaced by another ship from other series (such as the Nadesico from Martian Successor Nadesico series in Super Robot Wars J and Super Robot Wars W) as the part of the Three Ships Alliance.