The domino theory was a Cold War-era belief that if one country in a region came under the control of a communist government, then other countries in the region would also fall to communism, like a row of dominoes falling over. This theory was based on the idea that communism was an inherently expansionist ideology that would seek to spread to other countries.
American Fear of the Domino Theory
Americans feared the domino theory because they believed it would lead to the spread of communism throughout the world. They were particularly concerned that if Southeast Asian countries fell to communism, then Japan, Australia, and even the United States would be at risk. This fear was one of the main reasons why the United States became involved in the Vietnam War.
The Domino Theory in Practice
The domino theory did not always work out in practice. For example, although Cuba fell to communism in 1959, other Latin American countries did not follow suit. In fact, the spread of communism in the Western Hemisphere was largely limited to Cuba.
However, the domino theory did have some validity in other regions of the world. For example, the Soviet Union's invasion of Afghanistan in 1979 did lead to the spread of communism to other countries in Central Asia.
Conclusion
The domino theory was a significant factor in American foreign policy during the Cold War. It was based on a fear that communism would spread throughout the world and that the United States would be at risk if it did. While the domino theory did not always work out in practice, it did have some validity in some regions of the world.