High Quality Content by WIKIPEDIA articles! The Iron Duke-class was a group of four dreadnought battleships built for the British Royal Navy before the First World War. The class comprised four ships: Iron Duke, Marlborough, Benbow, and Emperor of India. Launched from October 1912 to November 1913, this was the third class of Royal Navy super-dreadnoughts. The ships were essentially King George V-class battleships; they retained the same ten 13.5 inch (34.3 cm) guns in five twin gun turrets on the centreline. However, the Iron Dukes had improved armour and a more powerful secondary armament of 6-inch weapons instead of the 4-inch mounted on the earlier ships.