Rapp was born on 20 April 1905 in Stockholm, Sweden, the son of Johan David Rapp, a wholesaler, and his wife Eva Hedvig Gustava. He passed studentexamen at Saltsjöbadens samskola in the spring of 1923 and became a sea cadet on 29 June 1923. Rapp took a naval officer exam on 5 October 1926 and became an acting sub-lieutenant in the Swedish Navy on 7 October 1926. He became a lieutenant there on 6 October 1928 and was then commanded to the Swedish Air Force on 1 November 1928. There Rapp became a lieutenant on 1 July 1930, and he then underwent the Royal Swedish Naval Staff College's general course from 1932 to 1933 and its staff course from 1934 to 1935. He served at the Organization Department of the Air Staff from 1 June 1935 to 1938 and became a captain in the Swedish Air Force on 30 June 1937. Rapp became a member of the board for the Defence Forces Central Civilian Employee Office on 1 January 1938 and division commander of the F 2 Hägernäs in 1938. He was acting head of the Organization Department of the Air Staff in 1941 and became head on 1 July 1943. Rapp was a member of the 1942 Reserve Officer Experts from June to November 1942 and he became a major in the Swedish Air Force on 1 July 1942 and a lieutenant colonel on 1 April 1944. He became commanding officer of Blekinge Air Force Wing on 23 June 1944 and was promoted to colonel on 1 July 1947. Rapp became Vice Chief of the Air Staff on 1 October 1948 and was a member of the Swedish Armed Forces School Study from June 1950 to March 1952. He was a member of the board of the Swedish Officers Association on 25 November 1950 and became commanding officer of the Fourth Air Group on 1 April 1951. Rapp became commander of the Third Air Group on 1 July 1954 and was promoted to major general on 1 October 1955. He became acting head of the Aircraft Department of the Royal Swedish Air Force Materiel Administration on 1 July 1956 and became a member of the board of the National Aeronautical Research Institute in 1957. Rapp was appointed Vice Chief of the Royal Swedish Air Force Materiel Administration and became a member of the board of the Swedish National Defence Research Institute on 1 October 1957. He was promoted to lieutenant general and became Chief of the Air Force on 15 January 1960. He was promoted to general and was Supreme Commander of the Swedish Armed Forces from 10 March 1961. During his time on the post, major changes were made to the Swedish defense, including a enhanced coordination between the army, the air force and the navy. The reorganization also meant that the Supreme Commander was given greater responsibility. Rapp left the post on 30 September 1970 and he was then general in the Swedish Air Force reserve from 1 October 1970 to 1981.
Personal life
Rapp married on 30 September 1933 in Stockholm with Ulla Gerda Maria Willers, the daughter of first secretary of the Royal Railway Board Johan Harald Hjalmar Willers and Agnes Lindberg. He was the father of Wilhelm, Lennart and Marianne.
Military career
In 1923 Rapp joined the Swedish Navy as a sea cadet
1926-1928 Acting Sub-Lieutenant Swedish Navy
1928-1930 Lieutenant Swedish Navy
1930-1937 Lieutenant Swedish Air Force
1937-1942 Captain Swedish Air Force
1942-1943 Major Swedish Air Force
1944-1947 Lieutenant Colonel, Wing commander Blekinge Air Force Wing
1947-1948 Colonel, Wing commander Blekinge Air Force Wing