More significant were the
V-1 flying bombs, codenamed 'Divers', which began to be launched against London from Northern France soon after the Allies launched their invasion of Normandy (
Operation Overlord) on
D-Day. V-1s (known to Londoners as 'Doodlebugs') presented AA Command's biggest challenge since the Blitz: the missiles' small size, high speed and awkward height presented a severe problem for AA guns. After two weeks' experience AA Command carried out a major reorganisation, stripping guns from the London IAZ, including 132nd (M) HAA Rgt, and repositioning them along the South Coast to target V-1s coming in over the English Channel, where the gun-laying radar worked best and where a 'downed' V-1 would cause no damage. The whole process involved moving hundreds of guns and vehicles and thousands of servicemen and women, but a new 8-gun HAA battery site could be established in 48 hours. After moving the mobile 3.7-inch HAA guns to the coast, these were progressively replaced by the static Mark IIC model, which had power traverse, accompanied by the most sophisticated Radar No 3 Mark V (the
SCR-584 radar set) and No 10 Predictor (the all-electric
Bell Labs AAA Computer). The guns were constantly in action and the success rate of the HAA batteries against 'Divers' rose progressively until late summer, when the launching sites in Normandy were overrun by
21st Army Group. ==Brussels 'X' deployment==