The Pathfinders were target-marking squadrons in RAF Bomber Command during World War II. They located and marked targets with flares, which a main bomber force could aim at, increasing the accuracy of their bombing. The Pathfinders were normally the first to receive new blind-bombing aids like Gee, Oboe and the H2S radar. The early Pathfinder Force (PFF) squadrons was expanded to become a group, No. 8 (Pathfinder Force) Group in January 1943. The initial Pathfinder Force was five squadrons, while No. 8 Group ultimately grew to a strength of 19 squadrons. While the majority of Pathfinder squadrons and personnel were from the Royal Air Force, the group also included many from the air forces of other Commonwealth countries. History Background At the start of the war in September 1939, RAF Bomber Command's doctrine was based on tight formations of heavily armed bombers attacking during daylight and fending off attacks by fighters with their defensive guns. In early missions over France and the Low Countries there was no clear outcome regarding the success of the bomber's guns: the Luftwaffe lacked widespread radar so their interception efforts were disorganized. On 18 December 1939, a raid by three squadrons of Vickers Wellington targeting ships in the Heligoland Bight was detected on an experimental Freya radar long before it reached the target area. The British bomber force was met by German fighters that shot down 10 of the 22 bombers, with another two crashing in the sea and three more written-off on landing. The Luftwaffe lost only two fighters in return. Although the causes for this disastrous outcome were heavily debated, it became clear that bomber forces could no longer defend themselves on their own. Bombing raids either needed to have fighter escort, which was difficult given the limited range of the fighters available at the time, or attacks had to be made at night when the enemy fighters could not see them. In the era before the widespread use of radar and the techniques needed to guide fighters to their targets with radar, night bombing would render the bombers vulnerable only if they were picked up by searchlights, a relatively rare occurrence. Offsetting the advantages of night bombing was the understanding that identifying the targets and attacking them accurately would be much more difficult. This meant a night bomber force was only useful against very large targets, like cities, and was one of