Why was the Gulf of Tonkin Resolution significant to the Vietnam War?

because it gave recently sworn in U.S. President Lyndon B. Johnson complete authorization to use military force in Southeast Asia.

Explanation:

roosevelt believed that in light of the country's recent military successes, it was unnecessary to use force to achieve foreign policy goals, so long as the military could threaten force. this belief, and his strategy of “speaking softly and carrying a big stick,” shaped much of roosevelt's foreign policy.

they were all fought in the middle east during ww1