Battle cruiser

A Battle Cruiser is a type of capital ship that is larger and more powerful than a Heavy Cruiser, but is smaller and has slightly less firepower and armor than a Battleship.

Specifically their roles are: Battle Cruiser classes in Starfleet are:
 * Heavy reconnaissance. Because of their power, Battle Cruisers could sweep away the screen of enemy cruisers to close with and observe an enemy fleet before using their superior speed to retire.
 * Close support for the fleet. They could be stationed at the ends of the fleet line to stop enemy cruisers harassing the formation's bigger starships, and to harass the enemy's lead ships if they were busy fighting their counterparts. Also, Battle Cruisers could operate as the fast wing of the fleet and try to outmaneuver the enemy.
 * Pursuit. If an enemy fleet ran, then the Battle Cruisers would use their speed to pursue, and their guns to damage or slow enemy ships.