Known locally in Oakville as "The Commodore," Robertson was appointed Commanding Officer of H.M.C.S. Fundy and Senior Officer of the first Minesweeping Flotilla in 1939. In 1941 he took command of one of Canada's Armed Merchant Cruisers, H.M.C.S. Prince Rupert. He was later made Commander of the Naval Dockyard and King's Harbour Master in Halifax.