 Young Zeiner-Henriksen became a member of the Norwegian Independent Company 1 ().From 1943 to 1944, he co-operated with Max Manus and Oslogjengen and, from 1944 to 1945, he participated in the Special Operations Executive operation GREBE in Dovrefjell and Rondane.He participated in the May 1944 sabotage of Arbeidstjenesten's offices.