The Germans arrested him when they occupied Norway.

Germany occupied Norway for five years, whereas Boyesen became a part of the resistance movement.

When the fighting subsided, and Germany occupied Norway, he was hired in the police, while at the same time conducting illegal resistance work.

The Germans occupied Norway until the German capitulation on 8 May 1945.

He was well protected on the north, where his troops occupied Norway and Denmark.

When Germany invaded and occupied Norway in 1940, the laboratory was closed.

When that occurred, the Allies would implement Plan R 4 and occupy Norway.