The readnought was the predominant type of battleship of the 20th century. The revolutionary HMS Dreadnought of 1906 adopted an 'all-big-gun' armament and steam turbine propulsion; her impact was so great that battleships built after her were referred to as 'dreadnoughts' and earlier battleships became known as pre-dreadnoughts. The only other major advance in kind was the US Navy design with all main turrets on the centerline of the ship.