What kind of support did the United States provide to China during the Second Sino-Japanese War?

During the Second Sino-Japanese War, the United States provided significant aid to China, aiming to bolster its war effort against Japan. This support included large shipments of arms and equipment, along with a military mission to advise on their use. The U.S. also implicitly agreed to help create a modern Chinese air force, maintain communication lines into China, and arm 30 divisions.1

Following Japan's attack on Pearl Harbor, the United States officially entered the war as an ally of China. Despite this alliance, China faced severe logistical challenges, including the loss of its primary supply routes like the Burma Road due to Japanese conquests. Consequently, much of the aid had to be transported via the perilous "Hump" air route over the Himalayas. While the U.S. provided equipment for groups like the Flying Tigers, which boosted Chinese morale, the overall military aid was comparatively limited, especially in the early years of the conflict. The U.S. also pressed for reforms in the Chinese army command structure to ensure more effective use of lend-lease supplies.1234