Final answer:
The Gulf of Tonkin Resolution in 1964 gave President Johnson the authority to escalate military operations in Vietnam without requiring a specific congressional declaration of war.
Step-by-step explanation:
The Gulf of Tonkin Resolution passed by Congress in 1964 granted President Lyndon Johnson the authority to escalate military operations in Vietnam.
The resolution was a response to reported attacks on U.S. warships in the Gulf of Tonkin, although later evidence revealed that the attacks did not actually occur.
The resolution gave President Johnson the power to retaliate against North Vietnamese attacks and to deploy troops without the need for a specific congressional declaration of war, leading to greater U.S. involvement in the Vietnam War.