He was born in Bergen as a son of ship-owner and captain Sigurd Mohn (1885–1959) and Margrete Oettinger (1893–1985).
During World War II he spent some years in exile in the United Kingdom.
He worked with psychological warfare and held the military rank of lieutenant, having been twice rejected as a fighting soldier (once during the Norwegian Campaign in 1940) due to his health.
After the war he was hired by Toralv Øksnevad as a Norwegian Broadcasting Corporation foreign correspondent.
[1] Notable documentary books include China i smeltedigelen (1950), Rød taifun over Korea (1951), Nassers nære Orient (1957), Nærbilde av Amerika (1964), Vietnam (1965), Tidsbomben Midt-Østen (1971), Tragedien Nord-Irland (1972) and Afghanistan kjemper (1981).