Severe communist losses during the Tet Offensive allowed U.S. President Richard M. Nixon to begin troop withdrawals. His plan, called the Nixon Doctrine, was to build up the ARVN, so that they could take over the defense of South Vietnam. The policy became known as "Vietnamization". Vietnamization had much in common with the policies of the Kennedy administration. One important difference, however, remained. While Kennedy insisted that the South Vietnamese fight the war themselves, he attempted to limit the scope of the conflict.

Nixon said in an announcement, "I am tonight announcing plans for the withdrawal of an additional 150,000 American troops to be completed during the spring of next year. This will bring a total reduction of 265,500 men in our armed forces in Vietnam below the level that existed when we took office 15 months ago."

On October 10, 1969, Nixon ordered a squadron of 18 B-52s loaded with nuclear weapons to race to the border of Soviet airspace to convince the Soviet Union that he was capable of anything to end the Vietnam War.

Nixon also pursued negotiations. Theater commander Creighton Abrams shifted to smaller operations, aimed at communist logistics, with better use of firepower and more cooperation with the ARVN. Nixon also began to pursue détente with the Soviet Union and rapprochement with the People's Republic of China. This policy helped to decrease global tensions. Détente led to nuclear arms reduction on the part of both superpowers. But Nixon was disappointed that the PRC and the Soviet Union continued to supply the North Vietnamese with aid. In September 1969, Ho Chi Minh died at age seventy-nine.

The anti-war movement was gaining strength in the United States. Nixon appealed to the "silent majority" of Americans to support the war. But revelations of the My Lai Massacre, in which a U.S. Army platoon raped and killed civilians, and the 1969 "Green Beret Affair" where eight Special Forces soldiers, including the 5th Special Forces Group Commander were arrested for the murder of a suspected double agent provoked national and international outrage.

The civilian cost of the war was again questioned when U.S. forces concluded operation Speedy Express with a claimed bodycount of 10,889 Communist guerillas with only 40 U.S. losses; Kevin Buckley writing in Newsweek estimated that perhaps 5,000 of the Vietnamese dead were civilians.

Beginning in 1970, American troops were being taken away from border areas where much more killing took place, and instead put along the coast and interior, which is one reason why casualties in 1970 were less than half of 1969's totals.