Mao was a pure psychopath....along with Stalin and Hitler he was about the most prolific killer of the 20th Century.All he was trying to accomplish was the gaining of total power....and adoration.Nothing more.Despite what he...or anyone else....might claim.
Right - Mao used the long march to eliminate his most powerful rivals within the Communist Party high command.
One of the things that's fascinating about PJ ORourke's piece is the story told to him by a survivor of the Long March, who was marching under the command of one of Mao's rivals, and whose comrades were systematically marched & starved to death by Mao so as to eliminate them as competitors to Mao [and his troops].
But sixty or seventy years later, when he spoke to PJ, this survivor still didn't realize that - that the Long March was so terrible for him & his comrades precisely because Mao was determined to [and succeeded in] killing them all off.
PS: Getting back to the story at hand, Mao used the entire "war" against Japan to attack Chiang in the countryside - Mao viewed the Japanese as his allies in weakening and deposing Chiang.