
After the outbreak of the Second World War that year, her remaining guns were removed to be used in shore defences. She was later used as a depot ship in Scapa Flow, starting in 1939. Two of her gun turrets and a good deal of her armour were removed, and her speed was reduced to 18 kn (33 km/h 21 mph) through the removal of some of her boilers.


She was demilitarised, to be used as a training ship. This duty assignment lasted 3 years, after which she was removed from active service. However, she remained with the fleet for a short time, having been transferred to the Atlantic Fleet in 1926. The Washington Naval Treaty of 1922 mandated that Iron Duke be removed from the active roster. During 1919–20, the ship operated in the Black Sea in support of the White Russians during the Russian Civil War. At Jutland, Iron Duke was assigned to the 3rd Division of the 4th Battle Squadron, and was stationed in the centre of the British line.įollowing the end of the war, Iron Duke was transferred to the Mediterranean Fleet. The ship took part in all of the major fleet actions, though only one of them ended in combat-the sortie on 31 May that resulted in the Battle of Jutland. After the outbreak of the First World War, the Royal Navy was reorganized the Home Fleet and the Atlantic Fleet were combined to form the Grand Fleet Iron Duke retained her position as fleet flagship, under John Jellicoe.

Upon commissioning, Iron Duke was assigned to the Home Fleet as the fleet flagship.
