What major conflict was influenced by the idea of the "Domino Theory"?

The major conflict influenced by the idea of the "Domino Theory" was the Vietnam War. This theory emerged during the Cold War and held that the spread of communism in one Southeast Asian country could trigger a chain reaction, or "domino effect," leading to the spread of communism in neighboring countries.

Specifically, U.S. leaders feared that if Vietnam fell to communism, surrounding nations like Laos, Cambodia, and even Thailand would also succumb, thus extending communist influence across the region. This fear prompted increased American involvement in Vietnam, including military support and ultimately direct military engagement, as the U.S. government sought to prevent what they perceived as a significant threat to freedom and democracy linked to global communism.

While other conflicts, such as the Korean War, also involved concerns about communism, the direct articulation and application of the Domino Theory are most closely associated with U.S. involvement in Vietnam. The other wars listed, such as World War II and the Gulf War, had different geopolitical contexts and motivations that did not directly invoke this theory.