When the term was originally conceived a century and half ago, a cruiser was a surface combattant capable of long-range independent combat against enemy warships up to the same size, but more importantly enemy merchant vessels of unlimited size. A cruiser was larger than the faster-moving but lighter armed frigate but smaller than the slower-moving but heavier armed battleship. Between the wars, arms limitation treaties split the vessel class into light cruisers (<=155 mm guns) and heavy cruisers (156-203 mm).
Some navies, for a period from just before the First World War to the start of the Second World War, built battlecruisers which had the speed and armour of cruisers but the size and armament of battleships. After the Second World War, France and Russia experimented with cruiser-helicopter carrier hybrids broadly similar to RP battlecarriers, but these were not tested in combat and have not adopted by other navies.
Since the end of the Second World War, as missiles have replaced guns, the roles of the cruiser have been largely borne by the destroyer. Today, only the United States, Russia, the Ukraine and Peru operate warships called cruisers; however, most destroyers in other navies are nearly the size of light cruisers fifty years ago.
Among conventional navies in NationStates, the cruiser is rarely the largest surface warship. Given its location under the water, Aqua Nation Atlantica has developed an underwarter cruiser type. A significant minority of NS navies use hybrid naval aviation-naval gunnery configurations on cruiser platforms. See the list of known NS naval cruisers below for details:
- Air Dominance Cruiser of Iluvauromeni Commonality of Everlasting Light, cruiser-aircraft carrier hybrid
- Andrea Venito Class Cruiser of Asgarnieu
- Ankara Class CGN of The Freethinkers
- Berlin Class CAN of The Freethinkers
- Bilyarsk Heavy Cruiser Sub of Aqua Nation Atlantica, submarine
- Community Vessel Cruiser of Sober Thought, cruiser-helicopter carrier-landing ship hybrid
- De Ruyter-class Battlecruiser of Knootoss
- Province-class Armored Cruiser of Hrydonia.
NationStates space forces
Generalisations are more difficult to make in the space force; consult list of known NS space cruisers below for details:
- Achilles class heavy cruiser of Bryn Shander
- Akira class starship of Eastasia, arguably a cruiser
- Conciliator Orbital Cruiser of Roudland
- Constellation class starship, arguably a cruiser
- Musai Daioh class light cruiser of Bryn Shander
- Spartan Class Cruiser of The Phoenix Militia
- Suiseiseki class light cruiser of Bryn Shander
- Usagi class heavy cruiser of Bryn Shander
- Viking Class Cruiser of The Phoenix Militia
- Marathon-class Cruiser of The United Nations Space Command