[1] Kempthorne was ordered from the Boston Navy Yard on 18 January 1942 as the Evarts-class destroyer escort Trumpeter (DE-279).

[2] After commissioning Kempthorne carried out training exercise in the Boston area in November before taking passage to Bermuda.

Throughout December she carried out further exercises and shore training, after which she sailed to Halifax, Nova Scotia to join convoy HX 274 bound for the UK.

[2] She then joined the Group at Belfast in April, serving alongside her sisters HMS Aylmer, Bickerton, Bligh, Grindall, Keats, Tyler and Goodson.

[2] Kempthorne first deployed with the group on 21 April, helping to escort the westbound convoy ONS-233 in appalling weather.

Fairey Swordfish of 825 Naval Air Squadron were scrambled from Vindex whilst Bligh, Bickerton and Aylmer carried out depth charge attacks.

In early June the group moved to the South Western Approaches to intercept U-boats which might be attempting to enter the English Channel to interfere with the landings.

After a period spent undergoing essential repairs and repainting, the group sailed to Scapa Flow on 12 August.

Kempthorne took off casualties and non-essential personnel, but it was later decided to scuttle Bickerton and she was sunk three hours after being hit.

In October they were deployed to escort a military convoy from the UK to Naples and on their return in December they were deployed in the North Western Approaches to intercept U-boats that had been forced by the advancing Allied armies to sail from the North German and Norwegian submarine bases to reach the Atlantic convoy routes.

They then began to search for another submarine known to be in the area, and posing a threat to the inbound convoy HX 332 as it passed through the Irish Sea bound for Liverpool.