[2] All of the V- and W-class destroyers, Walker among them, were assigned to the Grand Fleet or Harwich Force for the rest of World War I,[1] which ended with the armistice with Germany on 11 November 1918.
She remained in commission after the review as the fleet mobilised in the face of rising tensions between the United Kingdom and Nazi Germany; proceeding to Plymouth to prepare for wartime service.
[2] When the United Kingdom entered World War II in early September 1939, Walker was assigned to the 11th Destroyer Flotilla at Plymouth for convoy defence and patrol duties in the Southwestern Approaches.
While returning to Plymouth after detaching from the convoy, Walker and Vanquisher collided,[2] killing 14 men[4] about 200 nautical miles (370 km) southwest of Cape Clear Island, Ireland,[3] on 10[2] or 11[5] September 1939 (sources differ) with both ships suffering serious damage.
After detaching from OG 23, she, Campbell and Volunteer joined the sloops Scarborough and Wellington as the escort for Convoy HG 23 on the final leg of her voyage from Gibraltar to Liverpool, where she arrived on 30 March 1940.
[2] On 8 April 1940, Walker was transferred to the Home Fleet at Scapa Flow in the Orkney Islands to support operations during the Norwegian Campaign, escorting British military convoys carrying troops and equipment to the Nordic country.
On 28 May, she and the destroyers Beagle, Fame, and Havelock deployed in Norway's Rombaksfjord to provide gunfire support during an Allied ground operation to capture Narvik.
While rescuing them, Walker detected U-99 – commanded by another top German submarine officer, Korvettenkapitän Otto Kretschmer – attempting another attack on HX 112, and used depth charges to force her to the surface, after which her crew abandoned ship and scuttled her with the loss of three men dead,[7] at 03:43[7] or 03:48[3] hours (sources differ), at the approximate position 61°00′00″N 012°00′00″W / 61.00000°N 12.00000°W / 61.00000; -12.00000 (U-99).
[2] From 12 to 15 January 1942, Walker joined Vanoc, Volunteer, and the destroyer Witherington as the local escort of Convoy WS 15, consisting of 22 troopships bound – from the River Clyde in Scotland – for Suez, Egypt; Bombay, India and Singapore; during the first leg of her voyage in the Northwestern Approaches.
On 17 February 1942, she joined Convoy WS 16 – 21 troopships headed for Suez and Bombay – in the Clyde to serve along with Witherington, the destroyer Verity, and a large Home Fleet force consisting of the battleship Malaya, the aircraft carriers Eagle and Formidable, the light cruiser Hermione, and the destroyers Active, Anthony, Blankney, Croome, Duncan, Firedrake, Laforey, and Lightning, as escort.
In July 1943, she was assigned to the 4th Escort Group for convoy defence duties in the Northwestern Approaches and North Atlantic, which she continued until the end of the year.
From 7 to 12 April, Walker, Beagle, Boadicea, Keppel and the destroyers Inconstant, Venus, Westcott, Whitehall, and Wrestler escorted Convoy RA 58 during its voyage from the Kola Inlet to Loch Ewe, which the Germans did not detect.
[2] Selected for participation in Operation Neptune, the assault phase of the Allied invasion of Normandy which was scheduled for early June 1944, Walker upon her arrival in the United Kingdom, was assigned to Escort Group 137 along with the corvette Honeysuckle and the trawlers Lincolnshire and La Nantaise.
From 11 to 23 January, Walker, Keppel, and Westcott provided the close escort for Convoy RA 63 during its voyage from the Kola Inlet to the Clyde, a passage made in very bad weather that allowed only slow progress.
In March, she was assigned to antisubmarine warfare operations and convoy defence in the waters around the British Isles, continuing in this role until the German surrender in early May.