From Storm Clouds over the Pacific, 1931–1941, by Peter Harmsen (War in the Far East, Book 1; Casemate, 2018), Kindle pp. 116-118:
In January 1938, Russian pilot F. P. Polynin was still only a recent arrival in the central Chinese city of Wuhan, the de facto capital after Chiang Kai-shek had left Nanjing, and the Japanese invaders had still not got used to the idea that now they also had to fight the mighty Soviet Air Force. The 31-year-old officer’s squadron of high-speed, twin-engine Tupolev SB bombers was part of the Soviet aid that was beginning to trickle into China. On a cold morning shortly after New Year, his unit was put to the test with a difficult and dangerous mission into the heart of enemy country.
Polynin’s plane took off from the airfield before dawn, followed by 25 other bombers. Only they and a few other military personnel knew where they were heading: a Japanese air base near Nanjing, where a large number of aircraft had been assembled for a planned offensive. Secrecy among the Russians and Chinese had been tight, due to an all-pervasive fear of spies. The briefing of the crews had taken place behind closed doors protected by armed guards, to make sure no one was listening in.
The bombers crossed the Yangtze River under the dim light of the moon and reached their target just as dawn was breaking. The attack came as a total surprise to the Japanese. “Apparently they were still sleeping, because nothing was moving on the airfield,” Polynin wrote in his memoirs. “The Japanese aircraft were lined up as if for a review. Soon the bombs started falling. Fires broke out, and people were running back and forth among the flames.”
The operation went completely according to plan. Intelligence later showed that 48 Japanese airplanes had been destroyed in the raid. It was just one of many successes scored by the Soviet pilots assisting China in its desperate war against Japan. The aviators, part of the military aid to China promised in the wake of the bilateral Sino-Soviet agreement of the year before, had started making an appearance on the battlefield during the autumn 1937, and by 1938 their presence was of such a scale that it made up for some of Japan’s crushing superiority in the air.
A few weeks later, Polynin and his fellow airmen took part in an even more daring raid. This time the target was Formosa, a Japanese colony that the Chinese referred to by the old name of Taiwan. A total of 28 Tupolev SB bombers took off from Wuhan and crossed the narrow Taiwan Straits heading for the ocean north of the island. Once the aircraft had reached that area, they abruptly changed course due south, in the direction of Taiwan’s main city, Taihoku [= Taipei], and its military airport. Once again, Polynin was struck by the lack of preparation by the Japanese. “We could clearly see two lines of airplanes next to the hangars,” he wrote. “The enemy had done nothing to conceal the area. Obviously, he felt completely safe.” Polynin was in the lead plane, and releasing his bombs, he saw to his satisfaction one explosion after the other unfold like flowers in the middle of the airfield. The other planes followed suit, dropping a total of 280 bombs. Japanese anti-aircraft batteries opened up, but too late. All Soviet aircraft returned safely.
As time went by, Soviet pilots came to play a pivotal role in Chiang Kai-shek’s war effort. “We depended on the Russians,” a Chinese general said later. “Our pilots had been too brave at Shanghai. Our air force had been dealt too severe a blow.” The Russians were known for their courage and their devotion, spending most of their days in their cockpits, ready for take-off at seconds’ notice. Wherever they showed themselves in the big cities, they were treated as celebrities. In the countryside, they could not count on the same level of recognition. On the back of their jackets, Chinese characters stated: “I am a Russian. I am here to help you fight Japan.” It was a safeguard, perhaps even a life insurance, if they were shot down and parachuted down among suspicious Chinese peasants.