The Battle of Wuhan, popularly known to the Chinese as the Defence of Wuhan, and to the Japanese as the Capture of Wuhan, was a large-scale battle of the Second Sino-Japanese War. Engagements took place across vast areas of Anhui, Henan, Jiangxi, Zhejiang, and Hubei provinces over a period of four and a half months. It was the single largest, longest, and bloodiest battle of the entire Second Sino-Japanese War. More than one million National Revolutionary Army troops from the Fifth and Ninth War Zone were put under the direct command of Chiang Kai-shek, defending Wuhan from the Central China Area Army of the Imperial Japanese Army led by Shunroku Hata. Chinese forces were also supported by the Soviet Volunteer Group, a group of volunteer pilots from Soviet Air Forces.