Here are some specific gains for communism that contributed to these fears:
1. The Soviet Union's victory over Nazi Germany in World War II: This proved that a communist country could not only survive but also defeat a powerful capitalist country in war. It raised the prestige of communism around the world and made it seem like a viable alternative to capitalism.
2. The establishment of communist governments in Eastern Europe: After the war, the Soviet Union installed communist governments in a number of countries in Eastern Europe, including Poland, Czechoslovakia, and Hungary. This further expanded the influence of communism in the world and brought it closer to the borders of the United States.
3. The Chinese Civil War: In 1949, the Chinese Communist Party led by Mao Zedong won the Chinese Civil War and established the People's Republic of China. This was a major blow to U.S. interests in Asia and it further increased fears that communism was spreading at an alarming rate.
4. The Korean War: The outbreak of the Korean War in 1950 further fueled Cold War tensions and intensified Americans' fear of communism. Although not involving combat by American ground forces in China.
These gains for communism led to widespread fear in the United States that the country was losing the Cold War. This fear, combined with a lack of understanding of communism and a tradition of political persecution in the United States, created a climate of hysteria in which Senator Joseph McCarthy could thrive.