During World War II, The Enfield Cycle Company was called upon by the British authorities to develop and manufacture military motorcycles. The models produced for the military were the WD/C 350 cc sidevalve, WD/CO 350 cc OHV, WD/D 250 cc SV, WD/G 350 cc OHV and WD/L 570 cc SV. The most well known offering beyond doubt was the Flying Flea aka the Airborne. This lightweight 125cc bike could be dropped by parachute along with airborne troops. The factory also manufactured a variety of special instruments and apparatuses to use against enemy forces during war. In 1931, a four-valve, single-cylinder was introduced and christened "Bullet" in 1932. It had an inclined engine and an exposed valve gear. It was the very first use of the now famous Bullet name.