Another byproduct of the Japanese attack on Pearl Harbour was to allow US President Franklin Delano Roosevelt to send much more aid to China. While many in the United States and US Congress were friends of the Chinese and sympathized with them, many in the country were wary of getting involved in a war so far away. When the Japanese attacked the US directly, though, the gloves came off.

Before Pearl Harbor, President Franklin Roosevelt secretly authorized a group of fighter pilots and crewmen to fight the Japanese in China, either secretly or at least under ostensible Chinese command. This was the American Volunteer Group (the AVG), or more famously known as the Flying Tigers.

The AVG was under the direct command of retired American army officer Claire Chennault, who had essentially been forced out of the Army Air Corps because of his difficult nature and his bad hearing. Chennault was an accomplished pilot and had studied fighter tactics for some time, including being the head of an aerobatic team designed to perfect and display pursuit tactics and maneuvers. When he retired, he sought greener pastures in China, where, in the 1930s, the Chinese were hiring as many foreign military experts as it could to help in its fight against the Japanese. Chennault became one of a handful of American pilots, both civilian and ex-military, who helped the Chinese air force beginning in 1937. By 1938, Chennault was in charge of training all the foreign pilots helping the Chinese (with the exception of a number of Soviets, who operated secretly against the Japanese until they were recalled for the coming fight against Finland in 1939 and what was expected to be a coming war with Hitler).

Flying Tigers is a 1942 American black-and-white war film drama from Republic Pictures that was produced by Edmund Grainger, directed by David Miller, and stars John Wayne, John Carroll, and Anna Lee. The film dramatizes the exploits of the AVG, Americans who fought the Japanese in China, serving with the Chinese Nationalist forces, during World War II. The movie portrays them as fighting before U.S. entry into the war but, in point of fact, they did not see action until after the attack on Pearl Harbor. It is unabashedly a wartime propaganda film that was well received by a 1940s audience looking for a patriotic "flagwaver".