When the text states that dominoes fell after the Vietnam war what does this mean?

The phrase "dominoes fell" after the Vietnam War refers to the domino theory, which suggested that the spread of communism in one country would lead to its neighbors falling to communism as well, much like a row of dominoes toppling over. After the Vietnam War, this theory was used to explain how the fall of South Vietnam to communism in 1975 led to similar outcomes in other Southeast Asian nations, such as Cambodia and Laos. This concept highlighted the interconnectedness of geopolitical events during the Cold War era.