Alongside his preference for self-sufficiency and the importance of Chinese traditions, Mao was also quite aware of the importance of international conditions for the success of the Chinese Revolution. The Soviet Union was pivotal. To begin with:

The Soviet Union is a defender of world peace and a powerful factor preventing the domination of the world by the U.S. reactionaries Selected Readings, p. 348).

More specifically:

In the epoch in which imperialism exists, it is impossible for a genuine people’s revolution to win victory in any country without various forms of help from the international revolutionary forces, and even if victory were won, it could not be consolidated. This was the case with the victory and consolidation of the great October Revolution, as Lenin and Stalin told us long ago. This was also the case with the overthrow of the three imperialist powers in World War II and the establishment of the People’s Democracies. And this is also the case with the present and the future of People’s China. Just imagine! If the Soviet Union had not existed, if there had been no victory in the anti-fascist Second World War, if Japanese imperialism had not been defeated, if the People’s Democracies had not come into being, if the oppressed nations of the East were not rising in struggle and if there were no struggle of the masses of the people against their reactionary rulers in the United States, Britain, France, Germany, Italy, Japan and other capitalist countries — if not for all these in combination, the international reactionary forces bearing down upon us would certainly be many times greater than now. In such circumstances, could we have won victory? Obviously not. And even with victory, there could be no consolidation (Selected Readings, pp. 377-78).

As for the end of the Second World War and the surrender of Japan, Mao already saw what recent historians have rediscovered: Japan surrendered because Soviet troops pushed the Japanese out of China and threatened to invade Japan:

The decisive factor for Japan’s surrender is the entry of the Soviet Union into the war. A million Red Army troops are entering China’s Northeast; this force is irresistible. Japanese imperialism can no longer continue the fight … The Soviet Union has sent its troops, the Red Army has come to help the Chinese people drive out the aggressor; such an event has never happened before in Chinese history. Its influence is immeasurable. The propaganda organs of the United States and Chiang Kai-shek hoped to sweep away the Red Army’s political influence with two atom bombs. But it can’t be swept away; that isn’t so easy. Can atom bombs decide wars? No, they can’t. Atom bombs could not make Japan surrender. Without the struggles waged by the people, atom bombs by themselves would be of no avail. If atom bombs could decide the war, then why was it necessary to ask the Soviet Union to send its troops? Why didn’t Japan surrender when the two atom bombs were dropped on her and why did she surrender as soon as the Soviet Union sent troops? (Selected Readings, pp. 324, 337)