The escalation of American involvement in the Vietnam War can be traced to the domino theory, which suggested that the fall of one country to communism would lead to neighboring countries following suit. The Gulf of Tonkin Incident in 1964 prompted Congress to pass the Gulf of Tonkin Resolution, granting President Lyndon B. Johnson broad military powers in Vietnam. This led to the deployment of combat troops and a major increase in military presence. Subsequent events and policies further solidified U.S. commitment to combat communism in Southeast Asia, escalating the conflict.