Initially important to the Allied war effort because of plans to invade Japan from the Chinese mainland, it became mainly an effort to keep China supplied and in the war.  Allied forces, mostly British, Chinese, and Indian, engaged large numbers of Japanese troops that might have otherwise been used elsewhere.  The less than 3,000 volunteer soldiers who became famous as Merrill's Marauders, and the units of the Mars Task Force, were the only dedicated U.S. ground fighting forces in the Theater.

  America's role in CBI was to support China by providing war materials and the manpower to get it to where it was needed.  The majority of Americans in CBI worked to bring lend-lease supplies to China.  The Flying Tigers fought the Japanese in the air over China and Burma.  Army Air Forces flew supplies Over The Hump from India to China.  Merrill's Marauders and the Mars Task Force fought through the jungles of Burma.  Army Engineers built the Ledo Road to open up a land supply route.