DeWolf took command of HMCS "Haida" in August 1943. Under DeWolf, "Haida" earned a reputation as "the Fightingest Ship in the Canadian Navy", and was responsible for sinking 14 enemy ships in just over a year, earning numerous accolades. "Haida" and DeWolf saw service with convoys to Murmansk as well as operations to secure the English Channel in preparation for Operation Overlord. Most of his more famous battles took place at night in the English Channel, when DeWolf secured his reputation as a fearless and skilful tactician and became known to his crew as "Hard-Over-Harry" for bold manoeuvres off the coast of France. DeWolf earned the Distinguished Service Order for rescuing survivors of within range of enemy coastal guns on the French coast.