4 March
President Johnson met with the Joint Chiefs of Staff.
The Chairman of the Joint Chiefs of Staff General Maxwell Taylor recommended a "progressive and selective attack on targets in North Vietnam."
Johnson, however, disagreed, saying that "he did not want to start a war before November" because of the impact an expanded war might have on the Presidential elections that month.

15 March
In what one historian would describe as "the earliest expression" of "antiwar feeling among American college students" in response to the war, students at Yale University concluded a three-day long conference on socialism that included members of the new Students for a Democratic Society and launched the "May 2nd Movement" (M2M), and adjourned with plans for an antiwar demonstration in New York City for May 2, 1964.

16 March
Secretary of Defense McNamara wrote a memo to President Johnson after returning from his most recent visit to South Vietnam.
McNamara said that up to 40 percent of South Vietnam was now controlled by the VC, the Khánh government was ineffective, the South Vietnamese apathetic and the Americans in South Vietnam frustrated.
He recommended that the U.S. finance a 50,000 man increase in the size of the ARVN.
He also recommended that the United States Air Force (USAF) be prepared to initiate bombing of North Vietnam.
Johnson approved the plan and directed its implementation.

17 March
What would become known as the "domino theory" became the basis for American policy on Vietnam, after President Johnson approved National Security Action Memorandum 288 and the recommendations made to him by Secretary of Defense McNamara. "
We seek an independent non-Communist South Vietnam," McNamara wrote, adding that "unless we can achieve this objective... almost all of Southeast Asia will probably fall under Communist dominance", starting with South Vietnam, Laos, and Cambodia, followed by Burma and Malaysia. "
Thailand might hold for a period with our help, but would be under grave pressure.
Even the Philippines would become shaky and the threat to India to the west, Australia and New Zealand to the south and Taiwan, Korea, and Japan to the north and east would be greatly increased."

19 March
ARVN troops accompanied by U.S. Army advisers, mistakenly crossed the border into Cambodia and attacked the village of Chanthrea, killing 17 civilians.

26 March
Senator Wayne Morse was the only prominent American politician to oppose publicly American military involvement in South Vietnam.
Morse strongly disagreed with McNamara's assessment of the situation in Vietnam.
To refute McNamara's contention that the U.S. was fighting communism in South Vietnam, Morse said, "There are no Chinese soldiers in South Vietnam.
There are no Russian soldiers in South Vietnam.
The only foreign soldiers in South Vietnam are U.S. soldiers."

U.S. Army Captain Floyd James Thompson was captured by the VC after he and his pilot, Richard L. Whitesides flying in an O-1 Bird Dog, were shot down over Quảng Trị Province.
Whitesides was killed in the crash, while Thompson was sent to a prison camp in North Vietnam.
Released on 16 March 1973, Thompson remains the longest serving American prisoner of war.
4 March
President Johnson met with the Joint Chiefs of Staff. The Chairman of the Joint Chiefs of Staff General Maxwell Taylor recommended a "progressive and selective attack on targets in North Vietnam." Johnson, however, disagreed, saying that "he did not want to start a war before November" because of the impact an expanded war might have on the Presidential elections that month.
15 March
In what one historian would describe as "the earliest expression" of "antiwar feeling among American college students" in response to the war, students at Yale University concluded a three-day long conference on socialism that included members of the new Students for a Democratic Society and launched the "May 2nd Movement" (M2M), and adjourned with plans for an antiwar demonstration in New York City for May 2, 1964.
16 March
Secretary of Defense McNamara wrote a memo to President Johnson after returning from his most recent visit to South Vietnam. McNamara said that up to 40 percent of South Vietnam was now controlled by the VC, the Khánh government was ineffective, the South Vietnamese apathetic and the Americans in South Vietnam frustrated. He recommended that the U.S. finance a 50,000 man increase in the size of the ARVN. He also recommended that the United States Air Force (USAF) be prepared to initiate bombing of North Vietnam. Johnson approved the plan and directed its implementation.
17 March
What would become known as the "domino theory" became the basis for American policy on Vietnam, after President Johnson approved National Security Action Memorandum 288 and the recommendations made to him by Secretary of Defense McNamara. "We seek an independent non-Communist South Vietnam," McNamara wrote, adding that "unless we can achieve this objective... almost all of Southeast Asia will probably fall under Communist dominance", starting with South Vietnam, Laos, and Cambodia, followed by Burma and Malaysia. "Thailand might hold for a period with our help, but would be under grave pressure. Even the Philippines would become shaky and the threat to India to the west, Australia and New Zealand to the south and Taiwan, Korea, and Japan to the north and east would be greatly increased."
19 March
ARVN troops accompanied by U.S. Army advisers, mistakenly crossed the border into Cambodia and attacked the village of Chanthrea, killing 17 civilians.
26 March
Senator Wayne Morse was the only prominent American politician to oppose publicly American military involvement in South Vietnam. Morse strongly disagreed with McNamara's assessment of the situation in Vietnam. To refute McNamara's contention that the U.S. was fighting communism in South Vietnam, Morse said, "There are no Chinese soldiers in South Vietnam. There are no Russian soldiers in South Vietnam. The only foreign soldiers in South Vietnam are U.S. soldiers."
U.S. Army Captain Floyd James Thompson was captured by the VC after he and his pilot, Richard L. Whitesides flying in an O-1 Bird Dog, were shot down over Quảng Trị Province. Whitesides was killed in the crash, while Thompson was sent to a prison camp in North Vietnam. Released on 16 March 1973, Thompson remains the longest serving American prisoner of war.
1964 in the Vietnam War