Which congressional measure expanded U.S. involvement in Vietnam?

• A. Gulf of Tonkin Resolution
• B. Gulf of Tonkin Incident
• C. Tonkin Resolution
• D. Vietnam War Authorization

Answer: (A)

The key idea is a congressional measure that gives the president broad power to wage war without a formal declaration. After the Gulf of Tonkin incidents in 1964, Congress passed a resolution that stated the president could take all necessary measures to defend U.S. forces and prevent further aggression in Southeast Asia. This language effectively grants a “blank check” to escalate U.S. involvement, allowing expanded troop deployments, intensified bombing, and sustained military actions in Vietnam without a formal war declaration.

The Gulf of Tonkin Incident itself refers to the events that prompted the response, not the legislative action. Some sources call the same measure the Tonkin Gulf Resolution, but the specific authorization commonly named here is the Gulf of Tonkin Resolution. The term Vietnam War Authorization is too broad and not the exact historical label for this 1964 measure.