Commissioned into the Royal Navy in 1918, Peter Pelly served on HMY "Victoria and Albert" in 1939, but during the Second World War commanded HMS "Windsor" in 1940 when it was engaged in evacuating from Northern European ports. He was appointed an Officer of the Order of Orange Nassau for the role he played in this work, and was promoted to the rank of Commander in the navy in the same year. He was then attached to the 15th Cruiser Squadron off Crete and Malta and received the Distinguished Service Order (in 1942). From 1943 to 1945, he was with the Plans Division at the Admiralty and worked with the Cairo, Tehran, Quebec and Yalta Conferences. In the last months of the war, Pelly commanded HMS "Ameer" off Malaya.