During the Second World War, the government established a network of civilian airplane spotters whose duty it was to thwart any Axis sneak attack such as had befallen us at Pearl Harbor. From lonely observation posts throughout the coastal defense areas, the Army Air Forces Ground Observer Corps, numbering about 1,500,000 volunteers, maintained a vigilant and continuous watch on the skies over America to see that no hostile plains approached unnoticed. This volunteer air defense system was set up by the Fighter Command with the assistance of the American Legion, the OCD and other agencies, and established a new pattern of scouting. It remained in place until advancing technology in radar made them no longer necessary.