Following gunnery courses in 1916, 1918 and 1919 at the Royal Naval gunnery school (), Vian obtained a First Class certificate in Gunnery in October 1919. Despite being slated for service with the British Military Mission in Southern Russia, he was loaned to the Royal Australian Navy for two years from January 1920 and served as Gunnery Officer of , then the Australian flagship. On his return to the Royal Navy, Vian was given a series of appointments as gunnery officer, first, in January 1923, to the battleship , then serving as a cadet training ship. During this appointment, he was promoted to lieutenant-commander on 15 February 1924. This was followed in 1924 by two appointments to aging s ( and ). There was a short period at the Devonport gunnery school () and another sea posting, to the battleship in the Mediterranean Fleet in May 1925.