Marlborough served with the Grand Fleet for the duration of the war, primarily patrolling the northern end of the North Sea to enforce the blockade of Germany.

She saw action at the Battle of Jutland (31 May – 1 June 1916), where she administered the coup de grâce to the badly damaged German cruiser SMS Wiesbaden.

The damage to Marlborough was repaired by early August, though the last two years of the war were uneventful, as the British and German fleets adopted more cautious strategies due to the threat of underwater weapons.

The four Iron Duke-class battleships were ordered in the 1911 building programme, and were an incremental improvement over the preceding King George V class.

Close-range defence against torpedo boats was provided by a secondary armament of twelve BL 6-inch (152 mm) Mk VII guns.

[5] On the evening of 22 November 1914, the Grand Fleet conducted a fruitless sweep in the southern half of the North Sea to support Vice Admiral David Beatty's 1st Battlecruiser Squadron.

[6] Marlborough and most of the fleet initially remained in port during the German raid on Scarborough, Hartlepool and Whitby on 16 December 1914, though the 3rd Battle Squadron was sent to reinforce the British forces in the area.

[25] On 21 April, the Grand Fleet conducted a demonstration off Horns Reef to distract the Germans, while the Russian Navy relaid its defensive minefields in the Baltic Sea.

[26] The fleet returned to Scapa Flow on 24 April and refuelled, before proceeding south in response to intelligence reports that the Germans were about to launch a raid on Lowestoft.

The fleet sailed in concert with Rear Admiral Franz von Hipper's five battlecruisers and supporting cruisers and torpedo boats.

[32] The initial action was fought primarily by the British and German battlecruiser formations in the afternoon,[33] but by 18:00,[Note 2] the Grand Fleet approached the scene.

The transition from their cruising formation caused congestion with the rear divisions, forcing Marlborough and many of the other ships to reduce speed to 8 knots (15 km/h; 9.2 mph) to avoid colliding with each other.

[35] The British ships initially had poor visibility and Marlborough could only faintly make out a group of German Kaiser-class battleships at 18:17.

[37] During the engagement with Wiesbaden, the German cruiser launched one or two torpedoes at around 18:45, one of which struck Marlborough around the starboard diesel generator room.

At that time, the bulkheads in the starboard forward boiler room started to give way under the strain, forcing Marlborough to reduce speed to 12 knots (22 km/h; 14 mph).

Jellicoe detached the ship to proceed independently to Rosyth or the Tyne; Burney had ordered the scout cruiser Fearless to come alongside to transfer him to the battleship Revenge.

While there, her forward main battery and 6-inch magazines were emptied to lighten the ship, more pumps were brought aboard and the shoring supporting the damaged bulkhead was reinforced.

On the morning of 6 June, the ship left the Humber for the Tyne, where she would receive permanent repairs, escorted by four destroyers from the Harwich Force.

British signals intelligence decrypted German wireless transmissions, allowing Jellicoe enough time to deploy the Grand Fleet in an attempt to engage in a decisive battle.

The Grand Fleet sortied too late the following day to catch the retreating Germans, though the battlecruiser SMS Moltke was torpedoed and badly damaged by the submarine HMS E42.

Reuter believed that the British intended to seize the German ships on 21 June 1919, which was the deadline for Germany to have signed the peace treaty.

[59] On 12 March 1919, Marlborough was recommissioned at Devonport and assigned to the Mediterranean Fleet, as part of the 4th Battle Squadron,[9] along with her three sisters and two King George V-class battleships, Centurion and Ajax.

During this period, she served in the Black Sea during the Allied intervention in the Russian Civil War to support the Whites against the Red Bolsheviks.

The Empress refused to leave unless the British also evacuated wounded and sick soldiers, along with any civilians that also wanted to escape the advancing Bolsheviks.

On the morning of 12 April the ship anchored off Halki Island, about 12 miles (19 km) from Constantinople, due to doubt over the family's destination.

[66] While stationed off the Kerch Peninsula, the ship provided artillery support to White troops, including bombardments of Bolshevik positions in the villages of Koi-Asan and Dal Kamici.

[9] Following the Treaty of Lausanne in 1923, the Allied countries withdrew their occupation forces from Turkey; Marlborough was involved in escorting the troop convoys out of Constantinople.

[71] Marlborough briefly served as the flagship for the deputy commander of the 4th Battle Squadron after King George V was damaged from striking a rock off Mytilene.

The venting system worked as designed, and while the explosions caused serious internal damage, Marlborough was not destroyed, as the three battlecruisers had been at Jutland.

[77] Marlborough was placed on the disposal list in May 1932 and was quickly sold to the Alloa Shipbreaking Co. On 25 June, she arrived in Rosyth, where she was broken up for scrap.