The Gulf of Tonkin is a body of water that lies on the East Coast of North Vietnam and the West Coast of the island Hainan. This was the waters for the staging area of the U.S. Seventh Fleet, which included the American destroyers the Maddox and C. Turner Joy and the American aircraft carrier U.S.S. Ticonderoga. This was the site that would eventually lead the escalation and official documentation of U.S. involvement in Vietnam.
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On August 2, 1964, the Maddox was conducting a "DeSoto patrol", referring to an espionage mission. The purpose of this mission was to collect intelligence on radar and coastal defenses of North Vietnam. It was this day that the North Vietnamese torpedo patrol boats attacked the Maddox. The U.S.S. Ticonderoga sent aircraft to repel the North Vietnamese attackers and sunk one boat while damaging other enemy vessels.
In an attempt to possibly lure the North Vietnamese into an engagement, both the Maddox and the C. Turner Joy were in the gulf on August 4. The captain of the Maddox had read his ships instruments as saying that the ship was under attack or had been attacked and began an immediate retaliatory strike into the night. The two ships began firing into the night rapidly with American warplanes supporting the showcasing of the American firepower. However, the odd thing was that the captain had concluded hours later that there might not have been an actual attack. James B. Stockdale, who was a pilot of a Crusader jet, undertook a reconnaissance flight over the waters that evening and when asked if he witnessed any North Vietnamese attack vessels, Stockdale replied: "Not a one. No boats, no wakes, no ricochets [sic] off boats, no boat impacts, no torpedo wakes-nothing but black sea and American firepower." 
The entire event was purposely misconstrued when presented to Congress and the public by President Johnson and his administration, and on August 7, the "Tonkin Gulf Resolution" passed, 416 to 0 by the House and 88 to 2 by the Senate. The resolution stipulated that the President of the United States could "take all necessary measures to repel armed attack against the forces of the United States and to prevent further aggression." 
This was what led to the escalation of U.S. involvement in Vietnam and became the point where the U.S. made a large commitment. By July of 1965, the U.S. would have 80,000 troops mobilized and operating in South Vietnam. This opened the door to the eventual peak of some 543,000 troops by early 1969, including the dropping of 400 tons of bombs and ordnance per day. The Gulf of Tonkin Incident was a significant event in the fact that it opened the door to one of the most vivid and memorable wars in modern day history.