In April 1940 she patrolled the area south west of the Lofotens to screen the heavy ships against German U-boat attacks. In July, the destroyer assisted with the escorting of convoy WS-2 embarked were troop reinforcements including at least three Armoured Regiments for the 7th Armoured Division in Middle East. Also embarked was the 2nd West African Brigade en-route Mombassa for the Abyssinian Campaign. On August 25th, they arrived in South Africa, the convoy split into WS-2A for Cape Town and WS-2B for Simonstown, it included 14 ships. That same month the 8th DD Flotilla was transferred to Gibraltar, and destined for Force H. On September 6th, she sailed from Gibraltar with the fleet, in order to meet a troop convoy on the 13th, which was being escorted by two cruisers. The troops were to be deployed in the attack on Dakar. On the 24th of that month Fortune detected and sunk the French submarine Ajax. In October the destroyer was deployed in surveillance off the Morocan coast for suspected Vichy French warships.

January 1941 saw Fortune deployed as a convoy escort for a Malta bound convoy leaving Gibraltar, she was to steam as far as the Skerki Channel. On April 5th, she escorted the carrier HMS Ark Royal 400 miles off Malta, thereby enabling aircraft to be flown off to the island. On May 10th, whilst deployed as a unit of the covering force for a Malta bound convoy, Fortune received a heavy hit from German and Italian bombers and had to proceed back to U.K. for repairs. Once her repairs were completed she went back to Gibraltar.

In February 1942 Fortune was transferred from Gibraltar, to be based at Malta. After arriving at the island, she was tasked for convoy escort duties. April found the destroyer involved in Arctic convoy escort duties until June. By June she was once more back in the Mediterranean as a member of the 2nd DD Flotilla occupied in convoy escort duties. During March – April 1942 she was in the Indian Ocean as a member of force B under Vice Admiral Willis Eastern Fleet, based on Trincomalee, Ceylon. By June she was back in Mediterranean waters and again a member of the 2nd DD Flotilla. A double convoy was organised, one to sail from Gibraltar for Malta, and the other from Alexandria to Malta, Fortune being one of the many destroyers called in to assist in the escort duties. Fortune was slightly damaged to her rudder, this was repaired at Colombo. During September – November 1942 back in the Indian Ocean she was involved in the escorting of the aircraft carrier HMS Illustrious who was responsible for the supplying of air cover for the British occupation of Madagascar. December 7-15th saw Fortune docked in the Selborne dry dock at Simonstown, South Africa.

On 31 May 1943 HMS Fortune became HMCS Saskatchewan. In August 1943 Saskatchewan was a member of escort group C3 whose task it was to supply escorts in the north Atlantic, under the command of Cdr. Medley RN. She performed this function until the end of the year.

During June 6-30th 1944 Saskatchewan was a member of the 11th Escort Group, deployed against the U-boat threat to Operation Overlord.

During January – April 1945 HMCS Saskatchewan was detached from the Western Approaches Command for operations in Canadian waters, after undergoing repairs at Portsmouth. She was decommissioned on 27 January 1946 and sold to be broken up for scrap.