The Communist forces fought using guerilla warfare, while the Nationalist forces fought using positional warfare. The Nationalist forces occupied the major cities. The Communist forces had villages, and they were more organized. The used the countryside to deny the cities food, materials, and communication. They did not attack the Nationalist forces directly, until they were able to surround the Nationalists. The Americans aided the Nationalists heavily with money and equipment, but it was not used effectively. They had no loyalty among the soldiers, and the party was losing popularity. They ignored the pleas of the peasants and urban workers and didn't improve economic (eg. inflation) and political conditions. The Communists gained support because their soldiers were kind to the peasants. The Communists were on their own until they had some success. Then, the USSR provided aid. In the beginning, the Communists got their equipment from the Japanese and the Kuomintang.
The two revolutions occurred in relatively backward, agricultural and peasant based countries. The dynasties in both were weak. The nationalists in both revolutions made the mistake of regarding the urban aspect of the country as more important than the agricultural. Each had slogans that appealed to the masses, which were facing dire conditions. The Russian Revolution occurred because of worsening conditions due to WWI, and the Chinese Communist Revolution occurred after WWII. The distribution of land was used to attract support. The revolutions had single leaders with a devoted party. Republics emerged from the revolutions, although they were totalitarian states). There was massive propaganda for the new governments, and programs of indoctrination (schools) were introduced. The opposition was removed with purges. Farmland was gathered into collectives. Later on, 5-year plans were introduced. The two countries become powerful members of the global community, and this caused fear to those nations that were established as powerful.
This was the response Mao gave to the American threat. Mao believed that people, not weapons, decided the outcome of the war and China had one of the largest populations in the world. After the nuclear missiles, China would still have people to fight with, while the U.S. population was devastated. Therefore, the American nuclear threat (tiger) was not a real one, but one made out of paper (no real danger). The U.S. was only trying to scare people so that unwanted change would not occur. China aimed to break the nuclear monopoly of the nuclear powers.
Stalin aided Mao in this revolution. After its success, he immediately recognized the new republic. Stalin continued to aid China with money and arms. Stalin moved to make the PRC an ally. It gave up its claim to Port Arthur and its interest in Manchuria (move to stop hostility). Stalin also assisted in building the Chinese industry by setting up model factories, providing technical information, and...