How did the name "Hundred Regiments Battle" come from?

On August 20th, 1940, the Eighth Route Army launched a general attack on the Japanese traffic line.

On August 22nd, the headquarters of the Eighth Route Army successively received good news about the battles of various units. At noon, the Minister of Operations reported the actual combat situation of the troops to Peng, deputy commander, and Zuo Quan, chief of staff. The Minister of Operations said as many as a few treasures: Zheng Tai Road 30 Regiment, Pinghan Line Lugou Bridge to Handan 15 Regiment. ...

Hearing this, Zuo Quan suddenly said, "Well, this is a Hundred Regiments War. The War Department should carefully check the exact figures."

Peng said: "No matter whether it is more than a hundred regiments, it is called a hundred regiments war."

At noon that day, Peng and Zuo Quan indicated that the Battle of Zheng Tai was an unprecedented campaign launched by North China troops against the enemy on their own initiative since the Anti-Japanese War, with a total strength of about 100 regiments, hence the name "Hundred Regiments War" to expand external publicity.