The helicopter has been in military service since World War II, when Germany used light observation helicopters in small numbers. The first helicopters were relatively slow & dangerous, their inefficient piston engines having a less than ideal power to weight ratio. The invention of the turbine engine resolved many of the problems of piston engines The Aérospatiale Alouette II was the first production helicopter to use a turbine. Helicopters were invaluable during the many Post-War conflicts, especially in the jungle where parachuting in troops was difficult & dangerous. The US used helicopters extensively in Vietnam & suffered heavy losses to VC 12.5mm cannon.