An ancient design dating back to the Great Crusade the Chainsaw class was originally intended to escort convoys that were suffering heavy losses to raiders who were using bombers and interceptors to cripple ships before moving in to board them. The vessels and the attack craft groups they carried proved so effective that they soon found themselves on the frontlines of the crusade. They played key roles in many Imperial victories but unfortunately for the Imperium most of these vessels joined the forces of Chaos during the Horus Heresy with the bulk of the loyalist Chainsaws being lost in the conflict. Even worse much of the information regarding the design, including blueprints and even the location of the forgeworld where most of the class had been constructed, was lost.