An absorbing, frequently lyrical appreciation of radar's vital contribution to the Allied cause in WW II. Fisher characterizes radar as, without qualification, the single most important scientific/military invention of all time--not only the sine qua non of victory in the pivotal Battle of Britain, but also the bulwark of defensive systems that so far have prevented a third world war. With often ironic asides on circumstances and the principals, Fisher chronicles the under-the-gun development of RDF (radio direction finding) technology during the 1930's. Among the more notable personalities involved in the 11th-hour effort were Scots physicist Robin Watson-Watt and his largely unsung colleague, A.F. Wilkens, who created practical hardware for what was soon known as radar (radio detection and ranging). Also a hero is Hugh C.T. Dowding, the air marshall who championed radar early in the deadly game, oversaw installation of the Chain Home telecommunications network that made it an effective means of early warning, and led the gallant young pilots of RAF Fighter Command during their finest hour. Churchill is very nearly a villain of the piece, owing in part to perverse counsel from F.A. Lindemann, an influential advisor on scientific matters. Following Fisher's vivid account of radar's crucial role during the climactic summer of 1940 (when the Axis had still failed to realize, much less exploit, its potential), he provides accessible briefings on how, with US assistance, the technology was adapted for use in night-fighter aircraft and shipboard as well as airborne anti-submarine gear. He also reviews radar's postwar refinement and speculates on the lessons its original development may offer in the context of an atomic/spaceage arms race. In brief, then, a sharply focused and dramatically documented overview. The engrossing text has 16 pages of photographs (not seen), plus a wealth of schematic drawings that will help lay readers over the technical jumps.