Final answer:
The Gulf of Tonkin Resolution gave President Johnson the authority to escalate military operations in Vietnam without seeking a declaration of war from Congress.
Step-by-step explanation:
The Gulf of Tonkin Resolution, passed by Congress in 1964, gave President Johnson the authority to escalate military operations in Vietnam. This resolution granted him the power to use military force in Vietnam without seeking a declaration of war from Congress. It effectively increased the authority of the U.S. president and transformed the American role in Vietnam from advisor to combatant.