Close-range defence against torpedo boats was provided by a secondary battery of twelve BL 6 inch Mk VII guns. They were arranged in two superfiring pairs, one forward and one aft the fifth turret was located amidships, between the funnels and the rear superstructure. Iron Duke was armed with a main battery of ten BL 13.5 inch Mk V naval guns mounted in five twin gun turrets. Iron Duke had a crew of 995 officers and enlisted men, though during wartime this grew to up to 1,022. Her cruising radius was 7,800 nautical miles (14,446 km 8,976 mi) at a more economical 10 kn (19 km/h 12 mph).
The engines were rated at 29,000 shaft horsepower (21,625 kW) and produced a top speed of 21.25 kn (39 km/h 24 mph). Her propulsion system consisted of four Parsons steam turbines, with steam provided by eighteen Babcock & Wilcox boilers. She displaced 25,000 long tons (25,401 t) as designed and up to 29,560 long tons (30,034 t) at combat loading. Iron Duke was 622 feet 9 inches (190 m) long overall and had a beam of 90 ft (27 m) and an average draught of 29 ft 6 in (9 m). She continued to serve as an anti-aircraft platform for the duration of the war, and was eventually refloated and broken up for scrap in the late 1940s. In October, she was badly damaged by German bombers and was run aground to avoid sinking. She served in this capacity until the outbreak of the Second World War in September 1939, when she was moored in Scapa Flow as a harbor defence ship. Iron Duke was therefore converted into a gunnery training ship her armour and much of her armament was removed to render her unfit for combat. Iron Duke only remained on active duty for a few more years in 1930, the London Naval Treaty specified that the four Iron Duke-class battleships be scrapped or otherwise demilitarised. In 1926, she was assigned to the Atlantic Fleet, where she served as a training ship. She also assisted in the evacuation of refugees from Smyrna. She participated in both the Allied intervention in the Russian Civil War in the Black Sea and the Greco-Turkish War. After the end of the war, Iron Duke operated in the Mediterranean as the flagship of the Mediterranean Fleet. In January 1917, she was relieved as fleet flagship. There, she inflicted significant damage on the German battleship SMS König early in the main fleet action. Iron Duke served as the flagship of the Grand Fleet during the First World War, including at the Battle of Jutland. She was armed with a main battery of ten 13.5-inch (340 mm) guns and was capable of a top speed of 21.25 knots (39.35 km/h 24.45 mph). Launched ten months later, she was commissioned into the Home Fleet in March 1914 as the fleet flagship. She was built by Portsmouth Dockyard, and her keel laid in January 1912. HMS Iron Duke was a dreadnought battleship of the Royal Navy, the lead ship of her class, named in honour of Arthur Wellesley, 1st Duke of Wellington.