This is the true story of how in 1940 British scientists discovered and combatted the invisible beams that guided German bombers to their targets in the dark days of 1940 and then, turning the tables on the enemy, developed one of Britain's most successful secret weapons which was itself beam-based. Its name was Oboe. This ground-controlled blind-bombing system, introduced by No 109 Squadron into the Pathfinder Force, enabled RAF Bomber Command to pinpoint unseen targets with remarkable and previously unattainable accuracy. First as a dedicated wireless intelligence unit, next as a specialist squadron engaged in many forms of radio beam warfare, No 109 Squadron moved on to spearhead some of the most critical bomber operations of the war in Europe. Michael Cumming has discovered much revealing material to tell how No 109 Squadron, working with scientists at the Telecommunications Research Establishment (TRE) in a range of radar-based activities between 1940 and 1945, established a unique position in RAF and aviation history, pioneering new forms of precision bombing against key targets. Eyewitness accounts and archive photographs support the text.