On July 1, 1937, a border conflict erupted on the ancient marble Lugouqiao Bridge near Beijing between Japanese occupation forces in Manchuria and Kuomintang government troops. This incident triggered a full-scale war, which many historians consider the actual start of World War II, despite Japan’s hypocritical naming of it as the ‘Second Sino-Japanese Conflict’. The pretext was the absurd case of a Japanese soldier who went missing during maneuvers.
Following China’s rejection of their ultimatum, Japanese forces advanced from Manchuria deep into China. Beijing fell on July 28, Tianjin on July 30, followed by Kalgan and other cities. On August 13, battles began in Shanghai. The Aviation Committee of the Chinese government issued its Order No. 1 for air operations that same day, while the Japanese lacked airfields in the area, leaving their ground troops without air support.
The Outbreak of War and Japanese Air Superiority
The light aircraft carrier Hōshō, with its outdated A2N fighters, could not offer serious resistance. However, on August 15, the larger aircraft carrier Kaga approached the Chinese coast near Shanghai. Widespread air operations across Chinese territory began on August 14, but the air forces were inherently unequal. By this time, Japan’s state program for military aviation development and modernization, based on its own aircraft industry, was yielding significant results.
Between 1935 and 1937, the Japanese Air Force received an increasing number of combat aircraft: 952, 1181, and 1511, respectively. From 1937 onwards, Japan’s aviation industry operated under strict secrecy, sharply increasing the output of modern combat aircraft. By 1936-1937, the Japanese had independently designed and mass-produced twin-engine bombers like the Mitsubishi Ki.21 and G3M1, the Mitsubishi Ki.15 reconnaissance aircraft, the Nakajima B5N1 carrier bomber, and the Mitsubishi A5M1 (Type 96) carrier fighter.
The appearance of the A5M in Chinese skies in the autumn of 1937 was a significant event that was largely overlooked at the time. Until then, the capabilities of Japanese aircraft designers were widely underestimated in the West, where Japan’s aviation industry was thought capable only of copying Western designs. However, the A5M proved to be a fighter comparable in all respects to the best contemporary Western aircraft, becoming the main rival of the Chinese Air Force between 1937 and 1940.
Although Japan had only managed to re-equip its naval aviation by the start of the war, with its army aviation still undergoing reorganization, this was not a decisive factor. Operating from aircraft carriers and coastal airfields, and exploiting vast numerical superiority, Japan’s naval aviation quickly achieved complete air dominance. Long-range raids by naval bombers deep into Chinese territory from bases in Japan and Taiwan proved particularly valuable. The Chinese Air Force, conversely, was severely hampered by the absence of a truly operational aviation industry.
By the summer of 1937, the Kuomintang Air Force comprised about 600 combat aircraft, including 305 fighters, but less than half were combat-ready. Its squadrons were equipped with a mix of Curtiss Hawk IIs and IIIs, Italian Breda 27s, Fiat CR.32s, and outdated American Boeing 281s (P-26s). Despite the bravery of Chinese pilots in early engagements, losses were immense, and the Japanese A5M significantly outclassed the best Chinese fighter, the Hawk III. By October 1937, only about 130 aircraft remained, dwindling to some three dozen by November.
Soviet Aid: Operation Z and Logistical Challenges
In this desperate situation, Chiang Kai-shek’s government sought assistance from the USSR. On August 21, 1937, China and the Soviet Union signed a non-aggression pact and an agreement on military-technical assistance. In September, a decree was issued to supply China with 225 combat aircraft, including the highly effective Soviet I-15 (62 units) and I-16 (93 units) fighters, as well as 8 UTI-4 training aircraft, long before the official allocation of a $50 million credit tranche in March 1938.
This marked the beginning of the top-secret ‘Operation Z,’ which involved not only the supply of aviation equipment but also the deployment of Soviet volunteer pilots to participate in combat. At China’s request, squadrons composed of the best aviators were assembled, who, though believing they were headed to Spain, were sent to the ‘Sino-Japanese tea ceremony’. Selection took place across the country under strict confidentiality. Volunteers were briefed on the characteristics of the Japanese Type 95 (Ki-10) fighter.
By October 21, 1937, 447 personnel, including pilots, ground technical staff, and engineers, were ready for deployment to China. Pilots, dressed in civilian clothes, were sent by train to Alma-Ata. The ferrying of I-15s and I-16s took place via the ‘southern route’ (Alma-Ata to Lanzhou), while heavy equipment arrived by sea in Hong Kong, Haiphong, and Rangoon, followed by lengthy road or rail journeys through China’s underdeveloped transport infrastructure.
Ferry flights were conducted under extreme conditions. The small, poorly equipped high-altitude airfields on the ‘southern route’ were particularly dangerous for I-16s, especially given their high landing speed and the heavy load of fuel, ammunition, tools, and spare parts. Winter weather exacerbated the challenges, with snowfalls and sandstorms burying aircraft and requiring heroic efforts to clear runways. On October 28, a fatal accident claimed the life of group commander V.M. Kurdyumov during a landing at a Suzhou airfield.
Due to these losses and weather-related delays, the ‘air bridge’ was shortened. Fighters were disassembled and transported by truck to Hami, where they were reassembled, test-flown, and then ferried by air to Lanzhou. This 18-20 day route was crucial for delivering the first 62 I-15bis, along with bombs, ammunition, spare parts, fuel, and other specialized equipment. Kombrig P.I. Pumpur, commanding the southern route from October 31, 1937, improved pilot training for difficult landings, thereby reducing incidents.
Early Engagements and Tactical Evolution
Soviet pilots began fighting virtually from the moment they arrived at frontline airfields. On November 21, seven I-16s from the first group, despite having lost their commander Kurdyumov, shot down three Japanese aircraft (two Type 96 fighters and one bomber) over Nanking without losses. The next day, G.M. Prokofiev’s group achieved its first victory, downing a Japanese A5M in a six-on-six engagement. However, Lieutenant N.N. Nezhdanov died in air combat that same day.
By early December, volunteers conducted five sorties, shooting down and damaging about ten bombers and four fighters, losing two I-16s. On December 2, over Nanking, Soviet pilots shot down six bombers without losses, though the Japanese claimed to have shot down seven I-16s. Combat was initially intense and disorganized, with the Japanese continuously bombing Nanking, forcing pilots to fly five or six sorties daily against vastly superior enemy forces.
The Japanese Type 96 fighter was a new challenge for Soviet pilots, who had only studied the Type 95 prior to their deployment. Constant combat stress wore down the pilots, and losses mounted; two pilots died on the day Rykov arrived in Nanking in early December. The lack of clear leadership after Kurdyumov’s death affected organization. The arrival of Kombrig P.V. Rychagov, Hero of the Soviet Union, and Captain A.S. Blagoveshchensky gradually rectified the situation. Rychagov’s experience from Spain and Blagoveshchensky’s command abilities improved the initial disorganization.
Engagements became more organized, losses decreased, and Japanese aircraft shot down increased. Blagoveshchensky promoted effective tactics: attacking enemy formations from the tail, out of the sun, or over sparsely populated areas, flying in small, multi-tiered groups. A dedicated group would engage enemy fighters in combat. The successes of Soviet volunteers quickly made headlines in the world press.
By mid-December, the Chinese government requested increased aircraft supplies from the USSR. By spring 1938, China had received 94 I-16s, 122 I-15s, 8 UTI-4s, 5 UT-1s, 62 SBs, and 6 TB-3s, along with ammunition. Soviet pilots gained valuable combat experience that would later be applied in conflicts at Khalkhin Gol, Finland, and the Great Patriotic War. Blagoveshchensky also organized an air observation, warning, and communications service (VNOS) adapted to ‘Chinese realities’ and improved interaction between the fast I-16s and the more maneuverable I-15s.
At one pilot’s suggestion, he centralized machine gun firing by installing button triggers on control sticks. To lighten the aircraft, batteries were removed from all planes, and armor plates were installed on I-15s, saving many pilots’ lives. Early I-15 series supplied to China lacked armor backs, though Soviet technicians in Spain had improvised them. The I-15bis, a modified version incorporating combat experience, was tested in the USSR and later in China. I-16s were supplied in Type 5 and Type 10 variants; the Type 5’s firepower was enhanced with additional machine guns installed in China. By early August 1939, even 10 cannon-equipped I-16s were reportedly delivered.
Chinese aircraft markings already utilized large numbers for quick identification, an idea erroneously attributed to Blagoveshchensky. The first two digits indicated the squadron number, and the next two, the aircraft’s number within the unit. Chinese identification marks—a white-and-blue zebra stripe on the rudder and twelve-pointed stars on a blue background on the wings and fuselage—were applied to the aircraft in Lanzhou before their transfer to Chinese command. Only the black engine cowlings of fighters built at Moscow Aviation Plant No. 39 were repainted in a protective color.