Official History Of The Second World War Army Valuable title that covers in depth matters not considered in great detail in the main Military series Classified RESTRICTED post-war publication compiled by the authority of the Army Council, the object of which was to preserve the experience gained in weapon development during WW2. Scarce in it's original and only 1950 printing. Radar changed the Second World War.Radar could pick up incoming enemy aircraft at a range of 80 miles and played a crucial role in the Battle of Britain by giving air defences early warning of German attacks. The Allies had an important technological advantage with the the invention of the cavity magnetron in 1940, and equipment was developed rapidly for use in aircraft and ships and in land warfare.