The initial lineup of Chinese frontline fighter aircraft included but not limited to the Curtiss Hawk II, Hawk III, Boeing P-26C/Model 281, Fiat CR.32 among others. These engaged Japanese fighters, attack/bombers and reconnaissance aircraft in many major air battles beginning from 14 August 1937, when Imperial Japanese Navy's "Kisarazu Air Group" raided Jianqiao Airbase with the "schnellbomber" strategy, but suffering heavy losses; "814" has thus become known as "Air Force Day". Chinese Boeing P-26/281 fighters engaged Japanese Mitsubishi A5M fighters in the world's first dogfight between all-metal monoplane fighters. A long-distance "bombing raid" over Japan on 19 May 1938 saw two Chinese Martin B-10 bombers led by Captain Xu Huansheng fly into Japan, albeit dropping only anti-war leaflets over the Japanese cities of Nagasaki, Saga, Fukuoka, among others cities.