He is credited with being a co-founder of UNICEF and for his humanitarian efforts on behalf of Jews in the early years of World War II.

He also formed the humanitarian organization Nansenhjelpen in 1936 to provide relief for Jews fleeing Nazi persecution in central Europe.

[3][4] After returning to Norway, he joined the nascent Norwegian resistance opposing the government of Vidkun Quisling, he was arrested and detained by the Gestapo, and deported to the concentration camp at Sachsenhausen.

These diaries were published after the war and provide an in-depth account of life and death in Nazi concentration camps.

[7][8] He survived captivity in the camps and returned to Norway where he resumed his architectural career, while initiating several humanitarian efforts.