It started with the Gulf of Tonkin.
Two days later on August 4, Maddox and the destroyer Turner Joy both reported to be under attack again, by North Vietnamese torpedo boats; during this alleged engagement, Turner Joy fired approximately 220 3-inch & 5-inch shells at radar controlled surface targets.[6] Hanoi subsequently insisted that it had not launched a second attack. A later investigation by the Senate Foreign Relations Committee revealed that Maddox had been on an electronic intelligence (DESOTO) mission. It also learned that the U.S. Naval Communication Center in the Philippine Islands, in reviewing the ships' messages, had questioned whether any second attack had actually occurred.[7] In 2005, an internal National Security Agency historical study was declassified; it concluded that Maddox had engaged the North Vietnamese Navy on August 2, but that there may not have been any North Vietnamese Naval vessels present during the engagement of August 4. The report stated:
It is not simply that there is a different story as to what happened; it is that no attack happened that night.
https://en.wikipedia.org/wiki/Gulf_of_Tonkin_Resolution