The Iron Duke class was a group of four dreadnought battleships built for the British Royal Navy before the First World War.

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.

The four Iron Duke-class battleships saw limited active duty following the end of the war; they were all demilitarised under the terms of the London Naval Treaty signed in 1930.

[1] This was some 2,000 tons (2,032 tonnes) heavier than the preceding King George Vs, and was primarily due to the increase in calibre of the secondary battery.

This enabled a maximum range of 7,780 nautical miles (14,410 km; 8,950 mi) at a cruising speed of 10 kn (19 km/h; 12 mph).

The gun houses used were Mk II turrets that weighed 600 tons (610 tonnes) and allowed for depression to −5° and elevation to 20°.

The Mk V "Heavy" gun fired a variety of shells, including high explosive and armour-piercing rounds; they all weighed 1,400 lb (635 kg).

The guns were loaded with MD45 propellant charges that weighed 297 lb (135 kg); these were stored in silk bags.

At a range of 10,000 yd (9,144 m), the gun could penetrate up to 12.5 in (318 mm) of Krupp cemented steel armour, the type used on contemporary German dreadnoughts.

[6][Note 2] The secondary battery consisted of twelve 6-inch (15.2 cm) Mk VII guns mounted in casemates in the hull around the forward superstructure.

Admiral Jackie Fisher had opposed the idea of increasing the secondary battery, though he retired from the post of First Sea Lord in 1910.

This problem was compounded by the fact that they had been mounted too low in the hull, which subjected them to heavier pounding from rough seas.

The problem was eventually corrected by the addition of dwarf bulkheads in the gun houses and rubber seals to the hinged plates.

In 1914, two 3 in (7.62 cm) QF guns were fitted to the aft superstructure, primarily to defend against German airships.

[3] After the battle of Jutland in May 1916, some 820 tonnes of armour was added to the ships, primarily to thicken the deck around the main battery turrets, as well as to increase the bulkheads in the ammunition magazines.

[8] Upon commissioning, Iron Duke was assigned to the Home Fleet as the flagship of Admiral George Callaghan.

The ship took part in all of the major fleet actions, though only one of them ended in combat—the sortie on 31 May 1916 that resulted in the Battle of Jutland.

[2] 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.

Luftwaffe bombers attacked her on 17 October 1939; while they scored no direct hits, several near misses caused significant damage.

Like Iron Duke and Marlborough, Benbow was transferred to the Mediterranean in 1919, and she provided artillery support to White Russian forces in the Black Sea.