On December 20, 1941, the first battle of the American Volunteer Group, better known as the "Flying Tigers" in Kunming, China occurred. From the article:
"The American Volunteer Group (The “Flying Tigers”) | U.S. Embassy & Consulates in China
In April 1941, American President Franklin Roosevelt issued a secret executive order authorizing reserve officers and enlisted men to resign from the Army Air Corps, Naval and Marine air services for the purpose of serving in the American Volunteer Group (AVG) under the command of Claire Lee Chennault. Chennault divided his unit of 100 P-40 fighters into three squadrons, stationing two in Kunming and the third in Burma to protect China’s passage to the sea (Yu 38).
The AVG first saw combat on December 20, 1941 when ten enemy heavy bombers raided Kunming. AVG fighters intercepted the bombers, shooting down six and damaging three while sustaining no casualties of their own. With the support of Chinese code breakers and signal intelligence, the AVG continued to provide cover for Chinese ground forces and to defend Chinese cities against attacks by enemy bombers. Their exploits garnered them the legendary nickname the Flying Tigers.
The entrance of the United States into the Second World War meant that the American Volunteer Group was replaced by the American military. The group disbanded on July 4, 1942. By the end of its seven-month existence, the Flying Tigers of the American Volunteer Group had fought more than 50 air battles, and won them all. They destroyed 299 enemy planes at the cost of 12 of their own (Yu 45)."