Which event marked escalation of U.S. involvement in Vietnam in the mid-1960s?

• A. Tet Offensive
• B. Gulf of Tonkin Resolution
• C. Dien Bien Phu
• D. Paris Peace Talks

Answer: (B)

The key idea is how presidential authority expanded to commit more U.S. forces in Vietnam. The Gulf of Tonkin Resolution, passed in 1964, gave the president power to take all necessary measures to defend Southeast Asia, effectively authorizing a major expansion of American involvement without a formal war declaration. That blank-check style authorization allowed troop increases, sustained bombing, and a broader military campaign, marking the mid-1960s escalation.

Tet Offensive happened later, in 1968, and though it shocked the American public and influenced opinions, it wasn’t the moment of escalation itself. Dien Bien Phu occurred in 1954 and ended the French war, not U.S. escalation in the United States. Paris Peace Talks began in 1968–69 as discussions aimed at winding down the conflict, not escalating it.