During the first years, Kierkegaard devoted himself to flight service at the naval reconnaissance
Roslagen Air Corps (F 2) in ,
Östgöta Wing (F 3) in
Malmslätt and
Södermanland Wing (F 11) in
Nyköping. His specialty was
aerial reconnaissance, and he also served for a time as a reconnaissance pilot on the aircraft cruiser . During his service at Malmslätt, he made two visits to
Milan, Italy to take part in the repatriation of the Italian twin-engine bomber and reconnaissance aircraft
Caproni Ca.313, which in Sweden came to be called
B 16 and S 16. He attended the
Royal Swedish Naval Staff College's staff and communications course from 1945 to 1947, and then was promoted to lieutenant in 1947 and got his first commandership on the minesweeper . During the next two years, he came to participate in the extensive mine clearance operations that the Swedish Navy carried out after the end of the war. Kierkegaard served as a teacher at the Royal Swedish Naval Staff College from 1953 to 1957 and was promoted to lieutenant commander in 1956. During this time and was entrusted with service as captain of the destroyer as well as the newly built destroyers and . He developed a considerable knowledge of the action of hydrophone waves in the
brackish waters of the
Baltic Sea, and thus contributed to the development of the
anti-submarine warfare tactics. During the years 1957–1958, Kierkegaard was privileged to be the first Swede in the 20th century to undergo a command course at the
Naval War College in the United States. Back in Sweden, he was appointed head of the Naval Department in the
Defence Staff in Stockholm and was promoted to commander the following year. Kierkegaard was promoted to captain in 1963 and served as of commander of the 1st Destroyer Flotilla (
Första jagarflottiljen) from 1963 to 1965 when he assumed the post of vice chief of the
Southern Military District (Milo S) in
Kristianstad. Kierkegaard was promoted to rear admiral in 1970 and was appointed Commander-in-Chief of the
Coastal Fleet. He held the post for seven years before becoming commander of the
East Coast Naval Base in 1977, a post which he held until 1983 when he retired from active service. During his time as commander of the East Coast Naval Base, the
Hårsfjärden incident in the fall of 1982 occurred. ==Personal life==