1963 in the Vietnam War

January
The Battle of Ap Bac was a small-scale battle which resulted in the first major combat victory by the Viet Cong against regular South Vietnamese and American forces. The battle took place near the hamlet of Ap Bac, 65 km southwest of Saigon in the Mekong Delta. Forces of the 7th Division of the Army of the Republic of Vietnam (ARVN), equipped with armored personnel carriers (APCs) and artillery and supported by American helicopters, confronted entrenched elements of the Viet Cong 261st and 514th battalions.
 * January 2

June
The Hue chemical attacks was when soldiers of the Army of the Republic of Vietnam (ARVN) poured liquid chemicals from tear gas grenades onto the heads of praying Buddhists in Huế, South Vietnam. The Buddhists were protesting against religious discrimination by the regime of the Roman Catholic President Ngo Dinh Diem. The attacks caused 67 people to be hospitalised for blistering of the skin and respiratory ailments. Hòa thượng Thích Quảng Đức was a Vietnamese Mahayana Buddhist monk who burned himself to death at a busy Saigon road intersection on 11 June 1963. Thích Quảng Đức was protesting against the persecution of Buddhists by South Vietnam's Ngô Đình Diệm administration.
 * June 3
 * June 11

August
DEPTEL 243 was a high profile message sent on August 24, 1963 by the United States Department of State to Henry Cabot Lodge, Jr., the US ambassador to South Vietnam. The cable came in the wake of a series of bloody raids in which hundreds were believed to have been killed. The raids were orchestrated by Diem's brother Ngo Dinh Nhu. The message was the beginning of the end for Diem and historian John W. Newman described it as "the single most controversial cable of the Vietnam War."

September
The Battle of Go Cong was a small battle during the Vietnam War after the General Staff of the National Liberation Front called for "another Ap Bac" on South Vietnamese forces.
 * September 3

Maxwell Taylor, the Chairman of the Joint Chiefs of Staff, approves a plan (OPLAN 34A) for covert military raids in North Vietnam.
 * September 9

October
American troops in South Vietnam rise to 16, 732.

In National Security Council memorandum 263 (NSAM 263) John F Kennedy orders the withdrawal of 1000 American troops from South Vietnam. This policy is sometimes cited as part of a possible motive to assassinate Kennedy. (This theory is presented in Oliver Stone's film JFK.)
 * October 11

November
The arrest and assassination of Ngo Dinh Diem, then president of South Vietnam, marked the culmination of a successful CIA-backed coup d'état led by General Duong Van Minh. On the morning of November 2, 1963, Diem and his adviser, younger brother Ngo Dinh Nhu, were arrested and then killed in an armoured personnel carrier by ARVN officers.
 * November 2

New plans for Vietnam are drawn up at a military conference in Honolulu. Defense Secretary Robert McNamara approves OPLAN 34A.
 * November 20

President Kennedy is asassinated in Dallas. Lyndon B. Johnson becomes President of the U.S.
 * November 22

The Battle of Hiep Hoa was a minor battle of the Vietnam War. On the night of November 22, 1963, an estimated 500 Viet Cong soldiers overrun the Hiep Hoa Special Forces Camp, resulting in four American personnel MIA. The Battle of Chan La was a battle of the Vietnam War. The assault by Viet Cong forces was one in a series of attacks since the battle of Ap Bac back in January.
 * November 22
 * November 23

In National Security Council memorandum 273 President Lyndon B. Johnson reverses Kennedy's draw down and changes the goal of American involvement from supporting South Vietnam to defeating communist forces.
 * November 24