What is O'Brien referring to when he mention dominoes?

In "The Things They Carried," Tim O'Brien uses the metaphor of dominoes to illustrate the interconnectedness of events and the cascading effects of decisions made during the Vietnam War. The falling of one domino represents how a single action can trigger a series of consequences, reflecting the unpredictability and complexity of war. This imagery emphasizes the idea that individual choices can have far-reaching impacts, often leading to unforeseen outcomes.