The Orion-classbattleships were a group of four dreadnought battleships built for the Royal Navy (RN) in the early 1910s. The first 13.5-inch-gunned (343 mm)
BL13.5inch Mk V gun was a British heavy naval gun, introduced in 1912 as the main armament for the new super-dreadnought battleships of the Orion class
Orion-class dreadnought battleships, HMS Orion, HMS Monarch, HMS Conqueror, and HMS Thunderer, were the first British super-dreadnoughts. The Orion class