He was born in Bergen as a son of novelist and journalist Edvard Welle-Strand (1884–1964) and teacher Elsa Kielland, née Lindhé (1888–1979).
He worked briefly as a press secretary for the theatre Den Nationale Scene before studying at the University of Oslo.
He graduated from military college in 1943, then spent some time in an Officer Cadet Training Unit before serving on a Norwegian Motor Torpedo Boat (MTB).
He was then enrolled into the Norwegian Independent Company 1, and on 31 December 1944 he was parachuted over Hadelandsåsen to work as an agent in his home country.
[6]: 79 His main task was to secure important facilities, hereunder electricity and telecommunications, in case the Germans lost the war and would withdraw using a scorched earth tactic.
[2] Welle-Strand was married twice, first to a daughter of aide-de-camp and sports leader Nikolai Ramm Østgaard, then to language teacher.