In WWII, the allies developed electronic RADAR countermeasures systems to combat the German FLAK threat. The active electronic countermeasures equipment is called “Carpet”. Both Barrage and spot jamming systems were incorporated into the bombers. By wars end 2 barrage jammers (AN/APT-2) were installed in all non - PFF bombers and several bombers from each group had spot Jammers (AN/APQ-9) installed. The jammers and chaff reduced bomber losses by 75% during blind bombing missions.