After Germany invaded Norway in 1940, he participated in battles of the Norwegian Campaign. He joined Milorg where he was trained in weapons use by Svein Blindheim and William Houlder. In 1943, he joined Oslogjengen's Operation Bundle and obtained the status of an acting soldier in the Norwegian Independent Company 1, although he did not receive military training in the United Kingdom. He was arrested on 14 November 1944, and was incarcerated at Møllergata 19 until 30 December, then at Grini concentration camp until 8 May 1945. He was decorated with the Norwegian Defence Medal, the British Defence Medal and the St. Olav's Medal With Oak Branch.