Answer:
Between 1920 and until the early 1940s, the only communist country was the Soviet Union, where the first communist revolution, led by Vladimir Lenin, was successful in 1917.
From the early 1940s onward, communism began to expand rapidly to many areas in the world. For example, after the end of World War II, the Soviet Union expanded communism in Eastern European Countries like Poland, Hungary, and Romania, where it installed puppet governments.
In 1949, another important country became comunist: China. Led by Mao Zedong, the Chinese communists won the civil war against the Chinese nationalists (the Kuomintang, who later fled to Taiwan). In the same year, the Chinese People's Republic was proclaimed.
