Heavy Cruisers are a type of ship used by both the Alliance Fleet and the Syndicate World's Mobile Defense Force during the Alliance-Syndicate War. The primary mission of heavy cruisers is to destroy the lighter vessels of each fleet (destroyers and light cruisers in the case of the Alliance Fleet, and Hunter-Killers and Light Cruisers in the case of the Syndicate Mobile Defense Forces), serving as escort killers for the larger capital ships as they engaged one another during firing passes. Heavy Cruisers are fast enough to be sent along with Battle Cruisers and their smaller counterparts when detached operations are called for, and armored heavily enough that unlike Light Cruisers and the even lighter combatants available to each side, critical hits by Specter missiles and Hell-Lance fire do not necessarily lead to the immediate, catastrophic destruction of the ship. The Alliance Heavy Cruiser Merlon was one of the first Alliance ships destroyed in the conflict when an Alliance merchant convoy escorted by Geary's vessel was ambushed as it transited Grendel star system in one of the opening attacks of the war.