During the Second Sino-Japanese War and following the fall of Nanking in December 1937, Wuhan had become the provisional capital of China's Kuomintang government, and became another focal point of pitched air battles beginning in early 1938 between modern monoplane bomber and fighter aircraft of the Imperial Japanese forces and the Chinese Air Force, which included support from the Soviet Volunteer Group in both planes and personnel, as U.S. support in war materials waned. As the battle raged on through 1938, Wuhan and the surrounding region had become the site of the Battle of Wuhan. After being taken by the Japanese in late 1938, Wuhan became a major Japanese logistics center for operations in southern China.