Okamura was next military attaché to the puppet Japanese state of Manzhouguo (Manchukuo) in 1933 and 1934. He was then chief of the Intelligence Division of the army General Staff in 1935 and 1936. Promoted to lieutenant general in 1936, Okamura commanded the 2nd Division in Manchuria from 1936 to 1938. Okamura played an important role in the Sino-Japanese War as commander of Eleventh Army in China from 1938 to 1940. He was well informed regarding Chinese affairs, especially the Nationalist government of Jiang Jieshi (Chiang Kai-shek), and was reluctant to escalate the war.
Promoted to full general in 1941, Okamura headed the North China Area Army. In 1944, he became commander of the Japanese Expeditionary Army in China and launched Operation ichi-go, a major offensive in central and southeastern China, from mid-April 1944 to February 1945. Employing 410,000 troops, the Japanese made major territorial gains and realized their goals of eliminating U.S. air bases in China for the strategic bombing of Japan and opening land communications from north China to French Indochina. Okamura halted the advance because he feared the Soviet Union would enter the war against Japan.
Although Okamura and his 1 million Japanese soldiers in China had never been defeated by the Chinese, he surrendered unconditionally in Nanjing (Nanking) on 9 September 1945. After the war, Okamura was brought to trial by the Nationalist government of China. Okamura had developed close ties with members of the Nationalist government, so it came as no surprise when he was found innocent. He then worked with the Nationalist government from 1946 to 1948. The Chinese Communists tried to capture him, but Okamura escaped to Japan. In February 1950, Okamura arranged to send his former staff officers, known as the Pai Tuan (White Company) to Taiwan to assist the Nationalist government there. Kotani Ken
Coble, Parks M. Facing Japan: Chinese Politics and Japanese Imperialism, 1937–1941. Cambridge, MA: Harvard University Press, 1991.; Li, Lincoln. The Japanese Army in North China, 1937–1941: Problems of Political and Economic Control. New York: Oxford University Press, 1975.; Lindsay, Michael. The Unknown War: North China, 1937–1945. London: Bergstrom and Boyle Books, 1975.; Morley, James W., ed. The China Quagmire: Japan's Expansion on the Asian Continent, 1933–1941: Selected Translations from Taiheiyo senso e no michi, kaisen gaiko shi. New York: Columbia University Press, 1983.; Wilson, Dick. When Tigers Fight: The Story of the Sino-Japanese War, 1937–1945. New York: Penguin, 1982.