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. The Freshman operation was a failure, as the two gliders crashed. Another operation, called Gunnerside, was successful. The Gunnerside team joined the Grouse, and the combined team succeeded in the destruction of heavy water equipment and stock at Vemork in February 1943. After the sabotage Poulsson escaped to Oslo, and later via Sweden to the United Kingdom. Poulsson was awarded Norway's War Cross with sword, after his return to United Kingdom in 1943. It was presented to him by King Haakon at a ceremony at the training school STS 26 in Scotland, near Nethy Bridge. Also Rønneberg, leader of the Gunnerside team, received the War Cross with sword at this ceremony, while the other participants in the heavy water sabotage received the St. Olav's Medal With Oak Branch.
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 Telemark5 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. When Tronstad was killed in a shooting episode 11 March 1945, Poulsson took over as leader of the Sunshine operation.
In 1960 Poulsson was leading the Danish-Norwegian battalion in the UN forceUNEF in Gaza. From 1961 he held various leading positions in the Norwegian Army, and has been a colonel since 1968. He headed His Majesty The King's Guard from 1961-1965, he was second in command for Brigade Nord from 1967-1968 and he headed the 3rd Infantry Regiment from 1980-1982. Poulsson died early February 2010 aged 91. 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.
