Many squadrons and personnel from Commonwealth and other European countries flew in Bomber Command. No. 6 Group, which was activated on 1 January 1943, was unique among Bomber Command groups, in that it was not an RAF unit; it was a Canadian unit attached to Bomber Command. At its peak strength, 6 Group consisted of 14 operational RCAF bomber squadrons and 15 squadrons served with the group. No. 8 Group, also known as the Pathfinder Force, was activated on 15 August 1942. It was a critical part of solving the navigational and aiming problems experienced. Bomber Command solved its navigational problems using two methods. One was the use of a range of increasingly sophisticated electronic aids to navigation and the other was the use of specialist Pathfinders. The technical aids to navigation took two forms. One was external radio navigation aids, as exemplified by Gee and the later highly accurate Oboe systems. The other was the centimetric navigation equipment H2S radar carried in the bombers. The Pathfinders were a group of elite, specially trained and experienced crews who flew ahead and with the main bombing forces and marked the targets with flares and special marker-bombs. No. 8 Group controlled the Pathfinder squadrons.