China Burma India Theater (CBI) was the United States military designation during World War II for the China and Southeast Asian or India–Burma (IBT) theaters. Operational command of Allied forces (including U.S. forces) in the CBI was officially the responsibility of the Supreme Commanders for South East Asia or China. However, US forces in practice were usually overseen by General Joseph Stilwell, the Deputy Allied Commander in China; the term "CBI" was significant in logistical, material and personnel matters; it was and is commonly used within the US for these theaters. U.S. and Chinese fighting forces in the CBI included the Chinese Expeditionary Force, the Flying Tigers, transport and bomber units flying the Hump, including the Tenth Air Force, the 1st Air Commando Group, the engineers who built the Ledo Road, the 5307th Composite Unit (Provisional), popularly known as "Merrill's Marauders", and the 5332d Brigade, Provisional or 'Mars Task Force', which assumed the Marauders' mission. U.S. strategy for China Japanese policy towards China had long been a source of international controversy. Western powers had exploited China through the open door policy, advocated by United States diplomat William Woodville Rockhill, while Japan intervened more directly, creating the puppet-state of Manchukuo. By 1937, Japan was engaged in a full-scale war of conquest in China. The infamous Rape of Nanking galvanized Western opinion and led to direct financial aid for the Kuomintang (Nationalists) and increasing economic sanctions against Japan. In 1941, the U.S. made a series of decisions to support China in its war with Japan: Lend Lease supplies were provided after President Franklin D. Roosevelt announced the defense of China to be vital to the defense of the United States. Over the summer, as Japan moved south into French Indo-China, the U.S., Britain and the Netherlands instituted an oil embargo on Japan, cutting off 90% of its supplies. The embargo threatened the operations of the Kwantung Army, which had over a million soldiers deployed in China. Japan responded with a tightly co-ordinated offensive on 7/8 December, simultaneously attacking Pearl Harbor, the Philippines, Malaya, Singapore, Hong Kong, Guam, Wake Island, and Thailand. Japan cut off Allied supplies to China that had been coming through Burma. China could be supplied only by flying over the Himalaya mountains ("The Hump") from India, or capturing territory in Burma and building a new road—the Ledo Road. Burma In 1941 and 1942, Japan was overextended. Its naval base