 Matsui retired from active duty in 1935 but was called back into service in August 1937 at the start of the Second Sino-Japanese War to lead the Japanese forces engaged in the Battle of Shanghai. After winning the battle Matsui succeeded in convincing Japan's high command to advance on the Chinese capital city of Nanking. The troops under his command who captured Nanking on December 13 were responsible for the notorious Nanking Massacre.
