The Duncan class was a class of six pre-dreadnought battleships built for the Royal Navy in the early 1900s. The six ships—, , , , , and —were ordered in response to Russian naval building, specifically the fast second-class battleships of the , which they were specifically to counter. The foremost design consideration was a high top speed to match the rumoured (and incorrect) top speed of of the Russian ships while maintaining the same battery of guns and keeping displacement from growing. This forced significant compromises in armour protection, though the ships adopted a revised system of protection for the bow, which was copied in other designs like the .
All members of the class served in the Mediterranean Fleet after completion, thereafter joining the Home, Channel, and Atlantic Fleets over the next ten years. In 1906, Montagu was wrecked off Lundy Island and could not be salvaged. The period passed largely uneventfully for the other members of the class. Following the outbreak of the First World War in August 1914, the ships were sent to reinforce the Grand Fleet, where they were used on the Northern Patrol to help blockade Germany. In November, Russell and Exmouth bombarded Zeebrugge, but otherwise the Duncans saw no action in the first months of the war.
Cornwallis participated in the Dardanelles campaign beginning in early 1915, and most of the other members of the class joined her there over the course of the year. Duncan instead served in the Atlantic and later in the Adriatic Sea and Albemarle remained with the Grand Fleet and later went to Murmansk, Russia, to guard the port. Russell and Cornwallis were sunk by German U-boats in April 1916 and January 1917, respectively. The three surviving members of the class saw little activity in the final two years of the war, though Duncan and Exmouth were involved in the Allied intervention in Greece. All three ships were ultimately sold for scrap in the immediate post-war reduction in naval strength and were broken up in 1920.
Design
The six ships of the Duncan class were ordered in response to Russian s that began construction in the mid-1890s. At the time, the British mistakenly believed the Russian vessels were capable of a top speed of (though they were not that fast in service), so the Director of Naval Construction, William Henry White, set about designing a British response. His initial proposals were completed by February 1898, but the Board of Admiralty decided that more work would be required on the new ships, and so modified versions of the preceding would be ordered in the meantime. These ships incorporated some of the aspects of White's design, namely the revised armour protection layout in the bow, which abandoned the heavy transverse bulkhead that connected both ends of the armoured belt in favour of continuing the side armour all the way to the stem, albeit at reduced thickness; these became the five s. White then returned to working on the design for the response to Peresvet, completing a revised version on 14 June 1898.
To achieve the desired speed of 19 knots while keeping displacement about less than the Formidables and retaining the same battery of four guns carried by earlier British battleships, White was forced to make significant reductions, particularly in terms of armour protection. As such, they represented an evolution of the smaller , rather than a direct development of the Formidable or London types. The Duncan class was about a thousand tons heavier than the Canopus class, and with that increase in displacement, they acquired more powerful guns, heavier armour, and an improvement in top speed by one to two knots. Despite these improvements, the Duncans proved to be disappointments in service, owing to their reduced defensive characteristics, which rendered them inferior to the true first class battleships to which they were inevitably compared. Nevertheless, they were still markedly superior to the Peresvets they had been built to counter, and they were some of the fastest battleships in service at the time they were built.
Minor revisions to the dimensions were made between June and September, when the finalised design was approved, with tenders for shipyard contracts being sent out the following month. Public pressure over the 1898 programme—the first three Londons that were supposedly slower than the Peresvets—led to the passage of a Special Supplementary Programme that allocated funding for the first four Duncans, all of which were laid down in 1899. Two more were added under the 1899 programme.