At the beginning of the Sino-Japanese War in July 1937, Tanaka insisted on dispatching three divisions to China over the objections of General Ishiwara Kanji, chief of the Operations Division in the General Staff. After becoming a major general in 1939, he was appointed chief of staff of the Inner Mongolia Garrison Army and participated in the Battle of Nomonhan/Khalhin-Gol, in which the Japanese forces were defeated by the Soviets.
In October 1940, Tanaka became chief of the Operations Division of the General Staff. Promoted to lieutenant general in October 1941, he played a leading role in planning military operations leading to the Pacific war. Contrary to officials in the War Ministry, he favored an attack on the Soviet Union, and in late 1942, he also disagreed with them regarding military operations on Guadalcanal. He insisted on continuing the operations, but the War Ministry favored evacuation. During this controversy, Tanaka slapped General Sato Kenryo, chief of the Military Affairs Bureau, and verbally insulted Prime Minister General Tojo Hideki. In consequence, he was discharged from his post.
Assigned command of the 18th Division in northern Burma, from 1943 to 1944, Tanaka demonstrated superior leadership in adversity, fighting British forces under Brigadier General Orde Wingate and Chinese forces reorganized by Lieutenant General Joseph Stilwell. His outnumbered forces were gradually driven back. In September 1944, Tanaka was appointed chief of staff of the Burma Area Army. While traveling to Japan from Burma in May 1945, he was seriously injured in the crash of his airplane near Phnom Penh, Cambodia, and was still hospitalized in Saigon at the end of the Pacific war. Tanaka died in Kawasaki City on 24 September 1976. His memoirs were published posthumously in 1978. Tobe Ryoichi
Allen, Louis. Burma: The Longest War, 1941–1945. New York: St. Martin's Press, 1984.; Tanaka Shinichi. Tanaka Sakusen Bucho no Kaiso. Tokyo: Fuyo-Shobo, 1978.