1965 in the Vietnam War - Wikipedia

On November 14, 1965, the government sent 90,000 soldiers to Vietnam. From the article:

"In 1965, the United States rapidly increased its military forces in South Vietnam, prompted by the realization that the South Vietnamese government was losing the Vietnam War as the communist-dominated Viet Cong gained influence over much of the population in rural areas of the country. North Vietnam also rapidly increased its infiltration of men and supplies to combat South Vietnam and the U.S.. The objective of the U.S. and South Vietnam was to prevent a communist take-over. North Vietnam and the insurgent Viet Cong sought to unite the two sections of the country.

Political instability and internal dissent continued to plague the government of South Vietnam, although in June General Nguyễn Văn Thiệu and Air Marshall Nguyễn Cao Kỳ took control of the country and remained in power for the remainder of the year. In the United States, a majority of Congress and the people supported U.S. participation in the war, although protests against the war became larger and more frequent, especially among college students.

The U.S. began bombing North Vietnam in March, in Operation Rolling Thunder. The U.S. Army and Marines began ground operations to ferret out and defeat the communist forces. General William Westmoreland commanded U.S. forces in South Vietnam. Westmoreland's strategy was attrition, employing U.S. superiority in firepower, technology, and mobility. The usual military tactic of the United States was search and destroy operations in which large U.S. and South Vietnamese units, supported by air and artillery, swept through an area to attempt to engage the communists in battle. North Vietnam and the Viet Cong, by contrast, relied on hit-and-run operations and ambushes, avoiding set-piece battles except at their own initiative.

In November, the U.S. and North Vietnamese armies met head-on for the first time in the Battle of Ia Drang. Both sides claimed victory. The U.S. inflicted heavy casualties on the North Vietnamese, but the battle vindicated the conviction by North Vietnam that its military could slowly grind down the U.S.'s commitment to the war.

South Korea contributed an army division to South Vietnam, while Australia, New Zealand and other countries provided smaller numbers of soldiers. North Vietnam received military aid from the Soviet Union and China.

At year's end, President Lyndon Johnson declared a temporary halt to the bombing of North Vietnam and undertook a diplomatic initiative to seek negotiations with North Vietnam. North Vietnam, on its part, aimed to achieve a decisive military victory, but prepared also for an expanded war if the U.S. continued to escalate its involvement.

Most of the reports and conversations mentioned below were secret and not made public for many years. They reflect the ongoing debate among American officials, military leaders, and the American people about the scope and character of American intervention in the Vietnam War."