In the ideal form of the system, all of a battleship's armor is concentrated to form an armored "citadel" around the ship's magazine spaces. The citadel is an armoured box of uniform thickness designed to defend against the largest enemy guns. The propulsion plant, communications systems, weapons, ammunition stores, and command and control of the ship were located in a single area within and beneath the armored citadel. By stripping away the armor from all other parts of the ship, the armor of the citadel could be made thicker. Save for the turrets, the ammunition hoists, the conning tower and part of the steering gear, nothing in the way of armor protected the remainder of the ship. When battle stations were called, the whole crew retreated into this area behind armored bulkheads and armored, watertight doors.