 In the construction of the seaplane cruiser , his artillery knowledge was utilized, both during construction and his service as an artillery officer on board 1934-1936.Östberg's quick perception and determination made him fit and efficient as a staff officer.He served in the South Coast Naval District Staff in Karlskrona from 1936 to 1938, then as captain of the coastal defence ship HSwMS "Dristigheten" in 1938, and then as a staff officer in the Military Office of the Naval Defence ("Sjöförsvarets kommandoexpedition") from 1938 to 1942.