On 24 July 1943, days after the end of the Ruhr campaign, Harris ordered "Operation Gomorrah", an attack on Hamburg. The objective was to disrupt or end U-boat production in the port city.The introduction of "Window" blew a hole in German radar coverage and the bomber streams, aided by OBOE and H2S radar were able to penetrate the defences to devastate the centre of the city. The "Himmelbett" (canopy bed) system of radar-controlled night fighters slipping into the bomber stream and then using its own radar to pick out and engage individual bombers had gone. The effects of the raid, and the realisation German radar was temporarily blinded, led to the widespread use of the Wild Boar (Wilde Sau) tactics over the summer, 1943. Bomber Command reacted to Wild Boar operations by shortening the time bombers spent over the cities, use of Mandrel and "spoof" or diversion raids. Extended "Window" operations obscured radar and left German single-seat and engine fighters without any guidance for a time. NJG 2 failed to shoot down any RAF bombers. 12 bombers were claimed by night fighter pilots; nine by NJG 3 and three by NJG 1.