After his promotion to major general in July 1938, Tsuchihashi became chief of staff of the IJA 21st Army in August 1939, which was transferred to combat operations in the Second Sino-Japanese War as part of the China Expeditionary Army. The primary role of the IJA 21st Army was the Canton Operation (the invasion of Guangdong Province in southern China), together with the Imperial Japanese Navy’s 5th Fleet, which it completed by the end of the year. The IJA 21st Army was disbanded on February 9, 1940, and Tshuchihashi returned to Tokyo to become military liaison to the Chinese Embassy.