Twice in six weeks, in the late summer of 1964, U.S. destroyers reported they were under unprovoked attack, by North Vietnamese PT boats, while on patrol in the Gulf of Tonkin. The first incident produced a massive airstrike in retaliation, and three days later, the Gulf of Tonkin Resolution, which changed the course of the Vietnam War. The second attack produced...no response at all.  Did Lyndon Johnson learn something along the way?