As World War II broke out in Asia with the Battle of Shanghai and Battle of Nanjing, the Imperial Japanese Navy dispatched dozens of their unescorted Mitsubishi G3M bombers in the "schnellbomber" strategy of Giulio Douhet's "total war" concept of attacks against Chinese Air Force assets as well as civilian targets, however, the strategy backfired as the Japanese underestimated the effectiveness of the Chinese air raid early-warning net and the numbers of experienced Chinese pilots leading their squadrons of Curtiss Hawk III (max-speed marginally slower than G3M) and Boeing P-26 Model 281 (max-speed marginally faster than G3M) fighters in a bloody rout against the Japanese bombers. Nonetheless, the "total war" strategy with the "schnellbomber" wasn't lost to the Japanese, as the Chinese lost many of their top fighter pilots by Fall of Nanking at the end of 1937, and with ever-growing Japanese blockade of war materials and high-octane aviation fuel particularly following the capture of Nanning in the Battle of South Guangxi, the increasing obsolescence of Chinese fighter aircraft burning low-grade fuel versus fast and high-flying massed bomber formations burning high-octane avgas continued to wreak havoc and devastation against Chinese cities for years to come, particularly in the Battle of Chongqing and Chengdu beginning in May 1939; eventually however, the United States enacted an oil and steel embargo against Japan in July 1941.