HMS Iron Duke was the lead ship of the namesake class of four super-dreadnought battleships built for the Royal Navy in 1912. The class was the last British battleships to be equipped with 13.5 inch (343 mm) main guns. Iron Duke was laid down on 12 January 1912 at Portsmouth Shipyard, launched in October of the same year, and entered service on 10 March 1914. She served as flagship of the British Grand Fleet during World War I, participating in several battles against the German High Seas Fleet, most notably the Battle of Dogger Bank on 24 January 1915 and the Battle of Jutland between 31 May and 1 June 1916 — during the latter she managed to deal significant damage against the German battleship König. After the war, she was reassigned as flagship for the Mediterranean Fleet and participated in the Allied intervention in the Russian Civil War, and later took part in the final stage of the Greco-Turkish war in 1924, evacuating civilians during the Great Fire of Smyrna before serving as a host for the peace conference on board the ship.

Although the Royal Navy intended to modernise her, this plan was cancelled after the Washington and London Naval Treaty came into effect. As the ship was considered obsolete, she was demilitarised and converted into a gunnery training ship in the 1930s. At the outbreak of World War II in 1939, Iron Duke was moored at Scapa Flow to serve as a floating anti-aircraft platform, and was beached to prevent sinking a year later. She served in this capacity until the end of the war, after which her hull was scrapped in situ in March 1946.

HMS Iron Duke was introduced in Update "Kings of Battle". She is in her 1928 configuration and is therefore similar to her sister ship HMS Marlborough. She sports ten 13.5-inch guns with incredibly powerful HE shells that can deal good damage even against more advanced battleships, while the other shell choices are modestly effective against her equivalents. However, the 13.5-inch guns suffer from very long shell flight times, resulting in them being less accurate against evasive manoeuvres; this is further exacerbated by the limited range of her secondary 6-inch guns, which make ranging a target beyond 12 km difficult. In addition, much like her contemporaries, Iron Duke is slow and lacks anti-aircraft defences to fend off enemy aircraft.