The Japanese were aware of the results of the strategic bombing of Germany, and knew that the B-29 Superfortress would be bombing Japan and the resultant problems which would arise from trying to combat this. Japanese military attachés had become aware of the "Komet" during a visit to the Bad Zwischenahn airfield of "Erprobungskommando" 16, the "Luftwaffe" evaluation squadron charged with service test of the revolutionary rocket-propelled interceptor. They negotiated the rights to licence-produce the aircraft and its Walter HWK 509A rocket engine. The engine licence alone cost the Japanese 20 million "Reichsmarks" (equivalent to million euros).