The Gulf of Tonkin is a body of water located off the northeastern coast of Vietnam. It is bordered by Vietnam to the west and the island of Hainan, China, to the north. The gulf is significant for its strategic location and has been a site of naval activity throughout history. In August 1964, the Gulf of Tonkin Incident occurred, involving reported attacks on U.S. naval vessels by North Vietnamese forces. This event led to the passage of the Gulf of Tonkin Resolution by the U.S. Congress, which escalated American military involvement in the Vietnam War.