Following the German attack on the Soviet Union in June 1941, Sunde's group initiated sabotage activities in Norway. The group, consisting predominately of sailors, dockworkers and industrial labourers, was responsible for some 39 known actions between July 1941 and July 1944, dominating sabotage activity in Norway during this period. One of Sunde's cover names was "Osvald", and his group became known as the Osvald Group ("Osvald-gruppen"). The group's main area of operations was Buskerud.