He attended primary school in rural Furnes, but then moved to the nearby city Hamar to take apprenticeship as a typographer.
[6] He had a family background of interest in politics, as his father was a member of Furnes municipal council for the Liberal Party.
[7] Later, in 1915, the liberal workers' union Furnes Arbeiderforening under the chairmanship of Kristian Larssen decided to take up collective membership in the Labour Party.
He had nearly completed his training when being hired as sub-editor in the Labour Party newspaper Demokraten in June 1913.
Newly engaged to Aslaug Rustad, Larssen was hired in the Drammen-based newspaper Fremtiden in October 1916.
In 1940, when Norway became invaded and occupied by Germany, Larssen was the acting news editor of Arbeiderbladet before it was stopped by the Germans.
[15] He was held at Møllergata 19 from January to April 1942, then at Grini until February 1943, and thereafter in the Sachsenhausen concentration camp until the war ended.