The V-1 flying bomb was developed by Germany during World War II (1939-1945) as a vengeance weapon and was an early unguided cruise missile. Tested at Peenemünde-West facility, the V-1 was the only production aircraft to utilize a pulsejet for its power plant. The first of the "V-weapons" to become operational, the V-1 flying bomb entered service in June 1944 and was used to strike London and southeastern England from launch facilities in northern France and the Low Countries. When these facilities were overrun, V-1s were fired at Allied port facilities around Antwerp, Belgium. Due to its high speed, few Allied fighters were capable of intercepting a V-1 in flight.