of Shanghai and Battle of Nanking, pressing demands for aerial support at the Battle of Taiyuan in the northern front and Canton in the southern front, forced the Chinese Air Force to split the 28th PS, 5th PG based at Jurong Airbase in the Nanking defense sector into two smaller squadrons, and then dispatching half of the squadron to the south in Guangdong under the command of Lt. Arthur Chin, and the other half to the north at Taiyuan under the command of Capt. Chan Kee-Wong. Battle of Nanchang The Japanese launched pre-emptive airstrikes against Chinese Air Force assets at the Laoyingfang and Qingyunpu Airbases beginning in 1937; these were engaged by new Chinese Polikarpov fighters obtained under the Sino-Soviet Non-Aggression Pact of 1937. Summary of 1937 In the first four months of the war from July to November 1937, the Chinese Air Force flew 137 sorties, attacking Japanese army positions, and engaged in 57 air battles with Japanese airplanes; the Chinese Air Force shot down 94 Japanese planes and damaged 52 on the ground, but lost 131 aircraft. The Chinese Air Force pilots fought well despite their airfields being under constant Japanese air attacks. To commemorate the heroic acts and sacrifices of the Chinese pilots in defense of their homeland, the Republic of China declared 14 August the Chinese Air Force Day known as the "814 Day", the day on which the Chinese Air Force scored its first air-to-air victory. In this initial phase of the war, the outnumbered Chinese had no replacements for their lost planes and many experienced pilots killed in action, while the Western powers turned its back to the war situation, the Chinese began turning to the Soviet Union for new aircraft and various other combat equipment and war materials, while the Japanese were able to replace their lost planes with even more advanced aircraft, and continued to train new pilots. 1938 Battle of Taierzhuang Chinese B-10 bombers over Nagasaki The Chinese Air Force deployed two Martin B-10 (a.k.a. Martin Model 139) bombers led by pilots Capt. Hsu Huan-sheng and 1Lt. Teng Yan-po on 19 May 1938 in an infiltration mission over into Japan for the "leaflet bombing" of Nagasaki, Fukuoka, Saga, and other cities in the effort to solicit Japanese citizen's moral anti-war solidarity against Imperial Japan's violent aggressions and war crimes in China. Battle of Wuhan Battle of Guangzhou 1939 From mid-1938 to