anti-CCP propaganda ? we shouldn’t believe all CCP’s claims nor we should believe all KMT’s claims too. they had plenty of accusations against each other during their bitter struggle and not all of it is true by any means.
regarding the CCP’s participation in the anti-Japanese war. there are the KMT and CCP sides of the story, and the Japanese, American and Soviet accounts of the war too. we should read and consider all sides of the argument to have a better perspective on things.
the Soviets used the CCP as a significant leverage tool in their relations with KMT then. but the survival of the CCP mattered little to the Soviets who would undermine the CCP’s interests to improve their relations with KMT for their best interests. i don’t interpret it as Stalin favoring the KMT over the CCP.
Stalin would undoubtedly prefer to,install a pliant communist government in china that the Soviet Union can control. * But the immediate need of the USSR to win the war with Germany and then enjoy a decade or two of peace afterwards to rebuild outweigh that desire. *
Stalin favored KMT over CCP because it is KMT that could and did tie down the bulk of Japanese regular forces in china, and crippling Japan's ability to stab the USSR in the back as USSR fights for its existence against Germany. Stalin also had to favor KMT because it is the KMT that had the power to negotiate a peace settlement with japan that would stick and thus totally upset USSR's entire strategic posture after 1940. Finally Stalin must favor KMT over CCP because for much of the war, Stalin needed the solidarity of the US and UK, and the later considered KMT China's legimate government and would take a dim view of Soviet Union propping up a communist regime in china and thus upsetting their own plans for east Asia after the war.
In any case in orthrodox Marxist Leninist theorey Soviet Union embraced China's semi-feudal agrarian society is the type of society least suitable and least prepared by for proper communism, and therefore made the least promising candidates for successful communist takeover. Furthermore Stalin had his agents in yan'an and was in no doubt about Mao being pliant to soviet wishes. Mao would not have been stalin's preferred candidate for leading Chinese communist party onto a russocentric course. So this further devalued CCP in Stalin's eyes after Mao's takeover at Yan'an around 1942.
Stalin stabbed Mao in the back pretty clearly in 1945, when in return for KMT acquiescing to soviet sphere of influence in Outer Mongolia, the Soviet Union gave KMT full recognition as sole legitimate government of china, and gave KMT most of what the KMT wanted, including departure of soviet influence in xingjian, recognition that former soviet prewar possessions in manchurian belonged to kmt's china, and gave CCP almost no military support.