During World War II he was a Norwegian resistance member, especially noted for his role in the heavy water sabotage 1942–1943.

As a leader of the Grouse team he parachuted onto the Hardangervidda plateau on 18 October 1942, along with Arne Kjelstrup, Knut Haugland and Claus Helberg.

[5][6][7] The team landed at Fjarefit in Songadalen, and prepared to receive British troops of Operation Freshman at Møsvassdammen.

Nine SOE agents, among them several from the heavy water sabotage team, were paradropped over Ugleflott in Øvre Telemark 5 October 1944.

In the mountains surrounding Rjukan a military force consisting of 300 soldiers was built up, and the troops were supplied with provisions and weapons from allied aircraft.

In his funeral, King Harald V participated, in addition to historian Knut Werner Hagen, who is about to write a book about Poulsson in the near future.