Heavy water sabotage Poulsson served as a
second lieutenant in the
Norwegian Independent Company 1 () during
World War II. 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. The team landed at Fjarefit in Songadalen, and prepared to receive British troops of
Operation Freshman at
Møsvassdammen.
Operation Sunshine Poulsson returned to Norway in 1944, participating in
Operation Sunshine led by major
Leif Tronstad. Nine
SOE agents, among them several from the heavy water sabotage team, were paradropped over Ugleflott in
Øvre Telemark 5 October 1944. Their mission was to establish fighting groups at
Rjukan,
Notodden and
Nore. Poulsson, along with
Claus Helberg as wireless operator, was responsible for the Rjukan section. 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. The part of Telemark which was covered by
Sunshine was called
Milorg district 16 (D-16). When Tronstad was killed in a shooting episode 11 March 1945, Poulsson took over as leader of the
Sunshine operation (Milorg D-16). He was also decorated with the British
Distinguished Service Order (DSO) as well as the
St. Olav's Medal With Oak Branch. ==Post war==