Battlecruiser

A battlecruiser is a designation of capital ship used by human-led factions, such as the UNSC Navy. They have the hull classification code of CC. As the 'middle child' of heavy spatial combat ships, battlecruisers are envisioned to combine the raw fighting potential of battleships with the mobility of cruisers.

Characteristics
Battlecruisers are an anomaly in the human classification system. While most ships in this category have maximum mass of 25 million metric tons and a beam that exceeds two kilometres, this is not a hard rule that is enforced. Instead, they are defined as any capital ship that is primarily designed for ship-to-ship combat in space, is more heavily armed than a heavy cruiser, and is fast enough to still conduct fleet operations. Traditionally, this results in a larger hull that is armed with devastating main batteries, but sacrifices armour and weight in favour of retaining a high acceleration for their size. However, the term has also been applied to cruiser hulls with unusually-heavy weapons. The general rule of the thumb is that a battlecruiser is outmatched by a battleship of equivalent mass.

Because of their size, battlecruisers are normally deployed as flagships for larger naval formations, occasionally leading high-speed sorties. In combat, they excel at hunting down and crushing weaker forms of capital ships, which can include attack carriers, cruisers, and even other battlecruisers.

Large cruisers
Large cruisers (hull code: CB), also known as "super-heavy cruisers" by the media, is the name given to battlecruisers built to a specific design theory. Rather than arming themselves with individually more powerful weapons, they follow the principles used to design smaller cruisers. They generally have a somewhat more versatile construction, with larger numbers of smaller, lighter armaments, and using the saved weight to upgrade their armour. Because of this, they can fulfil the same niches their smaller cousins can, with their enhanced capabilities often putting them in command of cruiser squadrons.

Large cruisers were created during the Domus Diaspora as a compromise with politicians in the UEG Senate, who were often reluctant to fund the construction of battleships and battlecruisers in peacetime. Their heavy weapons were seen as unnecessary and inadequate against anything other than other capital ships. As a result, large cruisers were often the strongest ships the UNSC could devote to combat operations, supplementing carriers in the role of force projection. Prior to the Insurrection, dozens of ships in this class were commissioned by the UNSC Navy as a contingency measure against potential rogue CMA capital ships, a threat that would diminish as the rebellion escalated. During the war against the Covenant, they were slowly phased out and replaced by battlecruisers, as the light weapons often mean that they have to fight Covenant warships at dangerously-close ranges.

Large command cruisers
Large command cruisers (hull code: CBC) differ from their close relatives in that they have a large flag deck that accommodates the facilities needed for the ranking admiral and his staff. Often seen leading Numbered Fleets, these vessels are rarely built as original designs, and are normally modified from existing lines of battlecruisers and large cruisers at the time.