Kolmodin was born on 17 January 1896 in Bromma Parish, Stockholm, Sweden, the son of Professor Adolf Kolmodin and his wife Nelly . He was the brother of Colonel Gustaf Kolmodin and Diplomat Johannes Kolmodin. Kolmodin passed studentexamen in Uppsala in 1914 and was commissioned as an officer in the Swedish Coastal Artillery in 1916 with the rank of fänrik. He was promoted to Lieutenant in 1918. Kolmodin attended the general course of the Royal Swedish Naval Staff College from 1921 to 1922 and the senior course of the Artillery and Engineering College from 1922 to 1924. He served as an Adjutant in the staff of the commanding officer of the Swedish Coastal Artillery from 1925 to 1928 and as a mathematics, physics and artillery teacher at the Royal Swedish Naval Staff College and the Swedish Coast Artillery School from 1927 to 1937. Kolmodin then served in the Artillery Department of the Royal Swedish Naval Materiel Administration from 1928 to 1935. He also served as an expert in the 1930 Defense Commission from 1930 to 1935. Kolmodin was promoted to Captain in 1929 and to Major in 1936. He was appointed Chief of Staff of the Fortification Staff at Vaxholm Fortress in 1937 and in 1941 he was promoted to Lieutenant Colonel and first became Air Defence Commander at Karlskrona Fortress. When, during World War II, it was deemed necessary to provide the Swedish west coast with an effective coastal artillery defence, it was Kolmodin, who led the final expansion of this defence and gained command of it. He served as Commandant of Älvsborg Fortress in Gothenburg in 1941. In 1942, Älvsborg Coastal Artillery Regiment in Gothenburg was raised and Kolmodin was promoted to Colonel and became its first commander. He was at the same time commanding officer of Gothenburg Coastal Artillery Defence. Four year later, Kolmodin became commanding officer of Stockholm Coastal Artillery Defence and Defence District Commander of Stockholm Archipelago Defence District. In 1953, Kolmodin was promoted to Major General and appointed Inspector of the Swedish Coastal Artillery. Kolmodin was chairman of the 1958 Defense Command Commission and an expert in the 1960 Defense Command Inquiry. In 1961, Kolmodin retired from the military and was promoted to Lieutenant General.
Personal life
In 1934, Kolmodin married Baroness Christina Leijonhufvud, the daughter of Major General, Baron Gösta Leijonhufvud and Sigrid Lagercrantz.
