Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
On November 7, 1937 Japanese Central China Area Army (CCAA) was organized as a reinforcement expeditionary army by combining the Shanghai Expeditionary Army (SEF) and the IJA Tenth Army. General Iwane Matsui was appointed as its commander-in-chief, concurrent with his assignment as commander-in-chief of the SEF. Matsui reported directly to Imperial General Headquarters. After the Battle of Nanjing in December 1937, CCAA forces perpetrated the Nanjing Massacre, in which an estimated 200,000 people were brutally murdered. The CCAA was disbanded on February 14, 1938 and its component units were reassigned to the Central China Expeditionary Army.