Rather than a category of vessel, the designation "cruiser" originally meant the purpose or mission for the ship; to "cruise" long distances in escort, scouting, and raiding duties, or simply to provide an intermediate military presence where the deployment of larger, more expensive battleships were deemed strategically and financially unwise. The advent of steam power and steel accelerated the growth of the cruiser's development, discarding unwieldy, unreliable sails and wooden hulls for powerful engines and stronger hulls and components. Up to the opening stages of World War II, the various naval treaties — or their evasion thereof — created classes of cruisers such as "heavy cruiser", "battlecruiser", or "pocket battleship", reflecting their disproportionate firepower and performance in contrast to what the treaties were supposed to limit. In the present day, advances in technology meant that the destroyer could perform the duties that once required a cruiser's services more cheaply, efficiently and effectively, leading to its declining use in most navies today.
While the various nations had different mindsets when it came to the duties expected of cruisers, and outfitted them accordingly, cruisers can be considered the jack-of-all-trades, master-of-none class of warship. Almost all of them are able to adequately respond to changes in the battlefield and project considerable influence in the sector, outgunning anything they cannot outrun, and outrunning anything they cannot outgun; they are most commonly expected to act as destroyer and AA screens. A good cruiser captain watches the flow of battle and adapts to the circumstances as they unfold.
Each nation's cruiser line is unique in characteristics. The United States tends to have the best anti-aircraft defense as well as the best protection usually, with some exceptions. Japanese cruisers have powerful torpedo armament and the best high-explosive shells to set fires, but lack sufficient anti-aircraft defense and armor compared to the United States cruisers. Kriegsmarine cruisers have good range, high rate of fire, and good armor-piercing shells that inflict large amounts of damage and have good penetration for their size, but are weak in their high-explosive shell potential as well as their armor usually. Russian cruisers have the longest range and usually are good in both high-explosive and armor-piercing shells due to their high muzzle velocity, but have the poorest armor, insufficient anti-aircraft defense, largest detection range, and worst ship handling attributes compared to other nations. Finally, British cruisers consist exclusively of light cruisers throughout the line, with quick-firing, mid-caliber guns, generous compliments of torpedoes, and access to consumables that the other nations don't, but are hindered by exceptionally poor armor protection and mediocre anti-aircraft batteries.Cruisers come with a wide array of tools to help them adapt to many situations and can have up to four (4) slots for consumables, the most of any ship class (as with all other ships, the first slot will be filled with Damage Control Party). Hydroacoustic Search increases the range at which your ship can detect enemy ships and torpedoes, even through smoke screens; Defensive AA Fire increases the intensity (but not necessarily effectiveness) of a cruiser's anti-aircraft batteries, greatly reducing the performance of enemy aircraft unfortunate enough to be caught on the receiving end; Catapult Fighter launches fighter aircraft from the cruiser's catapults that escorts the cruiser and engages enemy aircraft that wander too close, although the effectiveness of a single aircraft against entire squadrons is understandably questionable (it's actually oddly effective); Spotting Aircraft allows a cruiser to extend the range of its main battery guns for a few minutes; Surveillance Radar detects enemy ships outside of their visibility range for a short duration; Smoke Generator provides cover where needed on the battlefield and obscures enemy vision; and at Tiers IX and X (Tier III for British cruisers), they receive access to the same Repair Party ability that battleships have, enabling them to regenerate some of the damage taken during battle.