After qualifying in gunnery Oswald joined the aircraft carrier in 1960. He was given command of the minesweeper in April 1962 and was promoted to lieutenant commander on 1 June 1963. After attending the Royal Navy Staff College in 1964, he was posted to the shore establishment HMS "Excellent" at Portsmouth as Air Weapons Officer in 1965. HMS "Excellent" maintains the gun carriage used for state funerals, and Oswald was the Funeral Gun Carriage Officer for the Funeral of Sir Winston Churchill on 30 January 1965. He was posted to the frigate HMS "Naiad" in September 1966 and promoted to commander on 31 December 1968 on his appointment to the Directorate of Naval Plans at the Ministry of Defence.