Within hours, Johnson ordered the launching of retaliatory air strikes (Operation Pierce Arrow) on the bases of the North Vietnamese boats and announced, in a television address to the American public that same evening, that U.S. naval forces had been attacked. In a message sent to Congress the following day, the President affirmed that "the North Vietnamese regime had conducted further deliberate attacks against U.S. naval vessels operating in international waters."
Johnson requested approval of a resolution "expressing the unity and determination of the United States in supporting freedom and in protecting peace in southeast Asia". He said that the resolution should express support "for all necessary action to protect our Armed Forces" — but repeated previous assurances that "the United States... seeks no wider war". As the nation entered the final three months of political campaigning for the 1964 elections (in which Johnson was standing for election), the president contended that the resolution would help "hostile nations... understand" that the United States was unified in its determination "to continue to protect its national interests.
On August 6, U.S. Secretary of Defense Robert S. McNamara testified before a joint session of the Senate Foreign Relations and Armed Services committees. He stated that the Maddox had been "carrying out a routine mission of the type we carry out all over the world at all times" and denied that it had been in any way involved in South Vietnamese patrol boat raids on the offshore islands of Hon Me and Hon Nieu on the nights of July 30 and July 31. The administration did not, however, disclose that the island raids, although separate from the mission of the Maddox, had been part of a program of clandestine attacks on North Vietnamese installations called Operation Plan 34A. These operations were carried out by U.S.-trained South Vietnamese commandos under the control of a special operations unit of the U.S. Military Assistance Command, Vietnam called the Studies and Operations Group.
After fewer than nine hours of committee consideration and floor debate, Congress voted, on August 10, 1964, on a joint resolution which authorized the president "to take all necessary steps, including the use of armed force, to assist any member or protocol state of the Southeast Asia Collective Defense Treaty requesting assistance in defense of its freedom. The unanimous affirmative vote in the House of Representatives was 416-0. (However, Republican Congressman Eugene Siler of Kentucky, who was not present but opposed the measure, was "paired" with another member who favored the resolution — i.e., his opposition was not counted, but the vote in favor was one less than it would have been.) The Senate conferred its approval by a vote of 88-2. Some members expressed misgivings about the measure, but in the end, Democratic Senators Wayne Morse of Oregon and Ernest Gruening of Alaska cast the only nay votes. At the time, Senator Morse warned that "I believe this resolution to be a historic mistake."
An investigation by the Senate Foreign Relations Committee revealed that the Maddox had been on an electronic intelligence collection mission off the North Vietnamese coast. It also learned that the U.S. Naval Communication Center in the Philippine Islands, in reviewing ships' messages, had questioned whether any second attack had actually occurred.
The administration of President Richard Nixon, which took office in January 1969, initially opposed repeal, warning of "consequences for Southeast Asia [that] go beyond the war in Vietnam". In 1970 the administration began to shift its stance. It asserted that its conduct of operations in Southeast Asia was based not on the resolution but was a constitutional exercise of the President's authority, as commander in chief of U.S. military forces, to take necessary steps to protect American troops as they were gradually withdrawn (the U.S. had begun withdrawing its forces from Vietnam in 1969 under a policy known as “Vietnamization”).
Rescinding the resolution ceased to be controversial, and a provision to repeal it was attached to a bill that Nixon signed in January 1971. Seeking to assert limits on presidential authority to engage U.S. forces without a formal declaration of war, Congress passed in 1973, over Nixon's veto, the War Powers Resolution, which is still in effect. It describes certain requirements for the President to consult with Congress in regard to decisions that engage U.S. forces in hostilities or imminent hostilities.