Royal Britannian MarinesEditNot much is known about the Royal Marines other than they serve as a branch for the navy, it is safe to say that the role of the Marines in the Code Geass universe is still the same as it were in the real world they are responsible for the use of Amphibious Warfare during missions and serving as the Ground Units for the Navy, they are only shown in screenshot during the first episode performing amphibious landing on the shore of Japan.
The Marines are most likely based on the the Royal Marines maintained by the United Kingdom in the real world, as they would have been active during the retreat from the British isles and the migration to the American continent. This would give them the role of commandos and rapid response units in their new modern setting.
Royal Marine Infantry (RMI)EditThe Royal Marine Infantry or RMI is the official designation for the Knightmare Corps. in the service of the Britannian Navy the RMI specialize in Naval and Amphibious Warfare although during Battle of Mt.Fuji a single unit of Portman II equipped with Float System can now participate in Aerial Combat but to what extend is not yet made clear, the Mechanized division is the equivalent of the Royal Panzer Infantry of the Britannian Army unlike the Royal Panzer Infantry the RMI receives little notice in the series and only appear in a few episode. In Area 11 the Navy was stationed in Shikine Island along side the RMI both of them is protecting the base from any Naval threat. The RMI staple Knightmare Frame is the Portman series.
Surface fleetEditTwo types of Britannian warship are shown. The most common are the Destroyers, which may have been modelled on the real-world Type 45 Destroyer. No class-name or ship names are given. Its armament includes a deck-mounted cannon and a vertical missile system, which can fire Asroc, though it may include missiles of other types. The other type is a larger Carrier-Battleship hybrid (search the Gallery). It is shown as having a trimaran hull, with the outboard hulls supporting two flight decks. It's armament includes two twin gun turrets, a vertical missile system, and numerous CIWS turrets, along with a complement of Portman knightmares. No names are given. All naval guns are shown to be cylindrical in shape and cross-section, implying that they are either conventional guns or electromagnetic coilguns.
Their main appearance is in R2 Turn 07 The Abandoned Mask (episode) which Suzaku attempts to chase down the Black Knights submarine with the help of a naval task force consisting of one Carrier-Battleship and at least 7-8 Destroyers. Suzaku's console screen shows a total of 32 ships, the bulk of which appear to be Destroyers.