Did Mao Zedong and Chinese communists collude with the Japanese during the Sino-Japanese War?

Question

Whilst answering another question on in which the CCP was militarily involved in the Sino-Japanese War, To what extent did the CPC avoid fighting with the Japanese? I came across groundbreaking and truly astounding information that the Chinese had apparently initiated a truce with the Japanese.

This was all done whilst the CCP spread propaganda about the GMD/KMT avoiding confrontation with the Japanese, running away in women's clothing ... so this all undermines their role in the war (or what little role they actually played), despite the current PRC claiming its greatness and bravery. From a Chinese standpoint, I believe this is vital information that shakes the foundation on which the PRC was established - Mao not only committed mass atrocities, he also betrayed the Chinese people - yet his portrait still hangs in the centre of Tiananmen Square. I am trying to demonstrate the significance of this.

I ask this question in hopes of further clarification on the incident; are there any different sources that also shed-light on this and confirm/assure credibility?

In the question, I used this source, http://www.japanpolicyforum.jp/archives/diplomacy/pt20160517095311.html, however, I find web discussion sources rather obscure, so I also found this Chinese language BBC report which talks about the same Japanese Professor as in the source above. http://www.bbc.com/zhongwen/trad/world/2015/12/151225_japan_professor_book - google can translate it to English, but so far I have not found an English version. I shall loosely translate some bits of the article: (please bear with my english)

In November 2015, Homare Endō, Professor of Tsukuba University, Japan, published her book Mao Zedong: the Man who Conspired with the Japanese in Japan.

[今年11月，日本筑波大學名譽教授遠藤譽撰寫的《毛澤東 與日軍共謀的男人》一書在日本出版。]

She quotes Iwai Iiyi's Recollections of Shanghai: "Contrary to Chinese official sources, the CCP agents obtained information on the Nationalist Revolutionary Army (NRA) through the United Front, only to hand it over to the Japanese, with the intention to weaken the GMD."

[但遠藤收集的岩井回憶錄《回想的上海》中則明確說，「事實完全相反，是中共特務把通過國共合作得到的蔣介石為首的國民黨軍隊的情報提供給日方，目的存在弱化國民黨的意圖」。]

Facing the invading Japanese in 1937, the Eighth Route Army and the New Fourth Army wanted to fight a war of resistance, but Mao Zedong insisted that only 10% of the troops should be committed to the Sino-Japanese War. Iwai Iiyi's Recollections of Shanghai also revealed that Pan Hannian [a professional spy from the CPC Central Intelligence Group’s Secret Service (Spy) Division.] had, through Yuan Shicheng, proposed to discuss the matters/arrangements for "truce" in the Northern [Chinese] regions. Because Iwai lacked skills/experience/knowledge in military matters, this proposal was handed over to Colonel Kagesa Sadaaki [who was Imperial Japanese Army General Staff]. From then on, Pan Hannian began directly communicating/being in contact with the Japanese military.

[1937年，面對入侵的日軍，中共八路軍和新四軍希望抗戰，但毛澤東則堅持只拿出10%兵力用於抗戰。岩井《回想的上海》還披露，潘漢年通過袁殊向岩井提議，商談共軍與日軍在華北戰場上「停戰」的事宜，岩井因不懂軍事，把該建議轉手影佐，潘漢年從此開始直接與日軍接觸。]

Answer 1

You may be overlooking the role of a "fourth" group of people: Chinese collaborators with the Japanese such as Wang Jing Wei.

Basically, the Japanese found many willing collaborators in former KMT-held territory, and none in Communist held territory. The Nationalist territory also held what was left of China's industrial capacity. Finally, when Japan decided on a "going south" strategy (against former European possessions in modern Vietnam, Myanmar, etc. instead of "north against Russian Siberia), nationalist territories offered a better link to the new Japanese conquests.

For all these reasons, Japan found Nationalist territories more lucrative than Communist territories. After 1941, Japan concentrated its efforts south, against Nationalist territories. The Communists were more than happy to acquiesce in this strategy; their doctrines called for seizing the more rural areas of the country (held by Nationalists), before the more urban areas (held by the Japanese). This led to an "implicit collusion" between the Japanese and the Communists.

Answer 2

Just by looking at the sequence of events you can ballpark whether the CPC was anti-Japan or was playing a part in the Romance of Three Kingdoms.

January 28 - March 02, 1932. Shanghai incident. KMT vs. Japan. Result: cease fire; KMT suffered 13,000 casualties including 4000 KIA.

March 22 - May 08, 1932. Su Jia Port battle. CPC vs. KMT. Result: Complete CPC vicotory. KMT lost 30,000 men, including 15,000 captured. CPC lost 500 men, captured 2000 rifles. Zhang Guotao, the CPC head, recounted this battle in his memoir, saying that Mao's guerrillas tactics were unfit because the KMT was playing defence and was hiding behind forts, and CPC commanders used siege tactics to lure and ambush KMT's reinforcements.

Needless to say, KMT's battle against Japan inspired neither admiration nor sympathy on the CPC side; the wounded beast was mauled again by its own kind.