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.

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.

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.

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 Formidable class would be ordered in the meantime.

[1] To achieve the desired speed of 19 knots while keeping displacement about 1,000 tonnes (980 long tons) less than the Formidables and retaining the same battery of four 12-inch (305 mm) guns carried by earlier British battleships, White was forced to make significant reductions, particularly in terms of armour protection.

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.

[2] 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.

[4] The ships' hulls were divided with longitudinal bulkheads that should have allowed for counter-flooding to offset underwater damage, but the equipment necessary to quickly flood a compartment was insufficient, as was typical in many British pre-dreadnought designs.

These were the same guns and mountings carried aboard the Formidable and London classes, although their barbettes were reduced in diameter as a weight-saving measure.

The guns had a muzzle velocity of 2,562 to 2,573 feet per second (781 to 784 m/s), and they were capable of penetrating 12 inches of Krupp armour at a range of 4,800 yards (4,400 m).

The designers considered moving two of the guns per side to the upper deck to improve their fighting capabilities in heavy seas, but decided that such an arrangement would hamper ammunition movement from the magazines.

Albemarle, Duncan, and probably Exmouth had theirs installed on their aft superstructure, while Russell had hers mounted on her quarterdeck and Cornwallis had her guns placed atop their forwardmost casemates.

Since the Duncans were intended to serve as fast battleships, White decided to reduce the risk of this kind of damage by discarding the forward transverse bulkhead in favor of a complete belt.

The main deck ran from the stem to the aft bulkhead and was connected to the top of the belt; it was 1 to 2 in thick, with the thicker armour over the central portion of the ship and the thinner steel over the bow.

The voids created between the decks and behind the belt were used to store coal, which had the added benefit of increasing the strength of the side protection layout.

Russell and Exmouth bombarded German-occupied Zeebrugge, which was being used as an advance naval base for U-boats, in late November, though they inflicted little damage and the Germans quickly resumed operations there.

[20] The ships were used to guard the southern British coast against German attacks through the end of the year, and in the first half of 1915, the 6th Squadron was gradually dispersed.

She participated in numerous attacks on the coastal fortresses guarding the Dardanelles, all of which failed to break through, leading to the Gallipoli Campaign, which Cornwallis also supported.

Fitted with heavy anti-torpedo nets, she was the only battleship stationed forward at Kephalo just outside the straits, owing to the increased threat of German U-boats in the area.

Russell was transferred to the Dardanelles campaign in November 1915; Albemarle was to have gone at the same time, but she was badly damaged in a storm and was unable to make the voyage.

Cornwallis met a similar fate on 9 January 1917, when she was torpedoed and sunk by U-32, though she remained afloat long enough for most of her crew to be evacuated by escorting destroyers; only fifteen men were killed in the sinking.