1955–1975: Vietnam War: U.S. military advisers had been in South Vietnam for a decade, and their numbers had been increased as the military position of the Saigon government became weaker. After citing what he falsely termed were Vietnam People's Navy attacks on U.S. destroyers, in what came to be known as the Gulf of Tonkin incident, President Lyndon B. Johnson asked in August 1964 for a resolution expressing U.S. determination to support "freedom and protect peace in Southeast Asia." Congress responded with the Gulf of Tonkin Resolution, giving President Johnson authorization, without a formal declaration of war by Congress, for the use of conventional military force in Southeast Asia.