Direct U.S. military involvement in Vietnam escalated dramatically following the Gulf of Tonkin incident in August 1964, when reported confrontations between North Vietnamese patrol boats and U.S. destroyers prompted Congress to pass the Gulf of Tonkin Resolution, granting President Lyndon B. Johnson broad authority to expand military operations without a formal declaration of war.
In March 1965, the first U.S. combat troops landed at Da Nang, initially assigned to protect the American air base there. Their arrival marked the beginning of a massive buildup, accompanied by the sustained bombing campaign known as Operation Rolling Thunder. By the end of 1965, roughly 184,000 American military personnel were in Vietnam, and that number continued climbing until it exceeded half a million in 1968, transforming what had largely been an advisory mission into a full-scale American ground war.
