Japanese invasion of French Indochina
19 September 1938, the 5th Division was subordinated to the 21st Army and sent to South China, participating in the Guangdong province offensive capturing Nanning in November 1938. The division was then ordered to return to North China on 29 November 1938 and subordinated to the 12th Army. Plans went awry because the 21st Infantry Brigade was surrounded by the Chinese in the Battle of Kunlun Pass in December 1938. As a consequence, these troops suffered heavy casualties and were delayed until late January 1939. The division returned to 21st Army in South China on 16 October 1939. The 21st Army was reformed to 22nd Army on 9 February 1940. As part of the newly-formed army, the 5th Division became the core of the forces allotted for the Japanese invasion of French Indochina on 22 September 1940. After the invasion, the division occupied the northern part of French Indochina.