When Congress passed the Gulf of Tonkin Resolution on 10 August 1964, which was the closest thing to a declaration of war that the United States had in Vietnam, Rostow was well pleased. About the Gulf of Tonkin incident that led to the resolution, Rostow later said: "We don't know what happened, but it had the desired effect". In November 1964, Rostow advised Johnson to commit U.S. ground forces to Vietnam to prove that "we are prepared to face down any form of escalation" and to send "massive" naval and air forces to strike North Vietnam and if necessary, China as well. In a memo to Johnson, Rostow wrote: "They Vietnamese Communists will not actually accept a setback until they are sure that we mean it" and needed to know that "they now confront a LBJ who has made up his mind".