the cross-Himalayan air-route known as "The Hump" – mostly destined for United States Army Air Force (USAAF) operations – and the Chinese Air Force were provided with new American Republic P-43 Lancer pursuit planes, which in theory with its very fast high-altitude performance and good firepower from its four 50 cal (12.7 mm) M2 Browning machine guns, was quite the upgrade the Chinese Air Force needed to effectively hit back at the Japanese raiders, but it was proven to be extremely unreliable and may have killed more of its own pilots than the enemies, including veteran pilot and 4th PG CO Major Zheng Shaoyu whose P-43 caught fire during a ferrying flight back to combat operations in China and was killed in the ensuing crash. Japan The majority of the Japanese air raids conducted against Chongqing and other targets around Sichuan were made with squadrons of medium-heavy bombers composed of IJNAF Mitsubishi G3M variants, known under Allied codename "Nell" and the IJAAF Mitsubishi Ki-21 "Sally"; others include the Fiat BR.20 Cicognas ("Ruth"), Kawasaki Ki-48 "Lily" and Nakajima B5N "Kate". Prior to the departure of the crack Japanese naval air units in China for the Pacific War in mid-late 1941, the new successor to the G3M bomber, the Mitsubishi G4M "Betty" and the Aichi D3A dive-bomber were operationally tested in the bombing of Chongqing, followed by newer designs such as the Mitsubishi Ki-67 "Peggy", Nakajima Ki-49 "Helen", and Yokosuka P1Y "Frances" (successor to the G4M), which were deployed in the following years as the bombing of Chongqing continued. Raids In the first two days of the Operation 100 (100号作战) bombing campaign, 54 and 27 Japanese bombers raided Chongqing on 3 and 4 May 1939 respectively, dropping approximately a 3:2 ratio of Type 98/25 high explosive "land bombs" (98 dropped on day one) and Type 98/7 incendiary bombs (68 dropped on day one). The first raid killed almost 700 residents and injured 350 more. Major Deng Mingde led the 22nd Pursuit Squadron (of the 4th Pursuit Group) Polikarpov fighters against the bombers on 3 May, shooting down seven bombers but losing two pilots including his deputy commander, the veteran Zhang Mingsheng. Zhang tried to save his damaged plane, but it became engulfed by fire, and while bailing-out and parachuting to safety, he was severely burned; he was then attacked by locals who thought he was a Japanese airman as he laid on