Orginally a TV tie-in expanded from the BBC televison series, the book covers the behind-the-scenes aspects of the fight by the "back room" scientists and technicians of WW2, including the battles against the Luftwaffe navigational beams, the V-1 and V-2 flying bombs, the development of radar, the battle against the u-boats, countering the magnetic mine, and the breaking of the codes produced by the Enigma machines.