A lot of mythology surrounds the Chinese Communist Party’s peasant origins and guerrilla tactics. But the Communist victory over the Nationalists in the civil war was not a mass uprising around the country, but a military campaign that started with victories in northeast China–Manchuria–and moved south from there. (There are some historical echoes, as when the Mongols and, later, the Manchus, conquered China, they also came from the northeast.) Here is Andrew Walder in his China Under Mao:

Victory was actually attained through conventional warfare fought between large modern armies, involving massive mobilization of material and human support for each side. Guerrilla warfare permitted the CCP to survive and expand during the Japanese invasion, but this survival strategy placed minimal demands on peasants to supply Communist partisans with food, material support, and recruits. Once the civil war began, the CCP abandoned guerrilla operations. As its armies poured into Manchuria after Soviet forces occupied the territory, Mao turned to a strategy of total mobilization for revolutionary war. The Red Army, renamed the People’s Liberation Army (PLA) in 1945, grew from 475,000 in 1944 to 2.8 million by 1948. …

The final years of the civil war resembled the Soviet army’s conquest of Eastern Europe in the last phases of World War II. The PLA rolled south from Manchuria and adjacent regions of North China, conquering vast regions that had never before been under CCP control, and regions like Tibet and Xinjiang that had not been governed by any Chinese state since the fall of the Qing dynasty.

Since the Communist victory was truly a military victory, many have looked to military causes to explain it. Chiang Kai-shek himself, in a book published after the war, focused attention on a series of events in 1946, around the city of Siping in Jilin province. Communist forces had occupied the city but were then dislodged by the Nationalists; at the same time, however, both parties were negotiating with the American envoy George Marshall, and a ceasefire was declared shortly afterward the Communist troops fled Siping. Chiang of course agreed to the ceasefire but in hindsight felt it was a mistake that allowed the Communists to regain the initiative:

This was a war that Chiang had lost in 1949, but which might have come out very differently, Chiang argued, if the Second Battle of Siping and its aftermath had been handled differently. The battle itself, Chiang said, had been “another decisive battle against the Communist troops.” As he described it, the three hundred thousand men under Lin Biao’s command had been utterly defeated: “More than half the Communist effectives became casualties.” Reports from the front, he said, “all agreed that barring some special international complications the Chinese Communists would not be able to fight anew after the terrific punishment they had just taken at the hands of the Government forces.”

Then there came the ceasefire and the suspension of [Nationalist general] Du Yuming’s pursuit of the Communist forces. Chiang believed that if his armies had continued their pursuit, “Communist remnants in northern Manchuria would have been liquidated.” Without a base area in northern Manchuria, the remaining Communist forces in Manchuria would have been deprived of Soviet support and “a fundamental solution to the problem of Manchuria would have been at hand.” Instead, “the morale of Government troops in Manchuria began to suffer” and Lin Biao rebuilt his forces in northern Manchuria. “The subsequent defeat of Government troops in Manchuria in the winter of 1948,” said Chiang, “was largely due to the second ceasefire order.” In this view, Siping was the decisive battle that could have been— if only a ceasefire, negotiated by George Marshall, had not intervened. Defeat had been snatched from the jaws of victory.

Chiang Kai-shek and Mao Zedong in 1945

That is from Harold M. Tanner’s The Battle for Manchuria and the Fate of China: Siping, 1946, which reconstructs the events leading up to and following the battle, and tries to answer the question of whether Siping was truly the turning point that ensured Communist victory in the civil war. While Senator Joseph McCarthy also blamed Marshall’s intervention for “losing China,” a number of more reputable historians have also seen Siping as a key turning point. Tanner however concludes that Chiang’s hope was a false one, in part because the Soviet Union was quietly but effectively supporting the Communists, and both the Nationalists and the Americans were afraid of getting into a direct confrontation with the Soviets:

The Truman administration had decided that while the United States would support Chiang Kai-shek, there would be limits to the extent of that support. Chiang desperately wanted the United States to take a more active role in supporting his government and his army in their struggle against what Chiang portrayed as the Soviet Union’s imperialist designs on Chinese territory. The Truman administration, however, was determined not to get directly involved in the Chinese Civil War, and especially not to challenge the Soviet Union by getting drawn into the struggle in Manchuria.

America was willing to transport Nationalist armies and to supply substantial amounts of weapons and ammunition, but, as we have seen above, American equipment alone could not give the Nationalists a substantial advantage on the battlefields of Manchuria. Even if the United States had been willing to do so, extending unlimited military aid to an army that was pursuing a fundamentally flawed strategy and a government that was proving incapable of winning the political struggle is not likely to have changed failure into success. In any event, the United States did not have unlimited resources to expend on Chiang’s government. Truman’s decision to limit support for Chiang was based on his assessment of American interests and capabilities, including American commitments elsewhere around the globe, and the very real possibility that American embroilment in China could lead to conflict with the Soviet Union.

Marshall’s decision to push for a ceasefire in June 1946 was made in this context, as well as on the basis of his assessment (backed up by the intelligence reports available to him) that the Nationalist Army was simply not capable of achieving victory in Manchuria. Chiang agreed to the ceasefire not only because Marshall was pressuring him to do so (although this was certainly an important factor), but also because he was aware of the limitations of his own armies, the challenges of further operations in North Manchuria, and the possibility that military operations north of the Songhua could elicit a dangerous reaction from the Soviet Union.

The Communist victory in China’s civil war, in this analysis, is ultimately the result of the Cold War and thus of how the Second World War ended. In fact, Peng Shuzhi, a Chinese Trotskyist, made much the same argument back in 1952:

Placed in an unfavorable position in the international situation created by the Second World War, American imperialism was obliged to abandon its aid to Chiang and its interference with Mao. At the same time, the Soviet Union, which had secured a superior position in Manchuria at the end of the war, inflicted serious damage to Chiang’s government and offered direct aid to the CCP. This enabled the latter to modernize its backward peasant army. Without this combination of circumstances, the victory of a party like the CCP, which relied purely on peasant forces, would be inconceivable.

For example, if Manchuria had not been occupied by the Soviet Union but had fallen entirely under Chiang’s control, Chiang Kai-shek would have utilized the economic resources and the Japanese arms in Manchuria to cut off direct connection between the CCP and the Soviet Union. This would have blocked the USSR’s armed support to the CCP. Similarly, the situation would have been quite different if direct intervention against the CCP by American imperialism had been possible. Under either of these two circumstances the victory of Mao Tse-tung would have been very doubtful.

To approach this from another direction, we could recall the defeat of the CCP’s peasant army in the Kiangsi period, 1930-35, when the bourgeois KMT’s power was considerably stabilized as a result of continual aid from imperialism, while the CCP was isolated from the Soviet Union. From this we can also derive sufficient reason to justify the conclusion that today’s victory of the CCP is entirely the result of the specific conditions created by the Second World War.