1972 in the Vietnam War saw foreign involvement in South Vietnam slowly declining. Three allies, Australia, New Zealand and Thailand, which had each contributed military contingents, left South Vietnam this year. The United States continued to participate in combat, primarily with air power to assist the South Vietnamese, while negotiators in Paris tried to hammer out a peace agreement and withdrawal strategy for the United States.
On 30 March North Vietnam launched the Nguyễn Huệ or Easter Offensive, a massive conventional invasion of South Vietnam. This led to a large increase in U.S. airpower and airstrikes to defend South Vietnam and a resumption of bombing of North Vietnam. By September the South Vietnamese had regained most of the territory lost in the offensive and the North Vietnamese returned to negotiations. Operation Linebacker II in mid to late December saw intensive bombing around Hanoi and Haiphong.
January 1 January U.S. military personnel in South Vietnam numbered 156,800 while Free World Military Assistance Forces (largely Republic of Korea Army) numbered 53,900.
The South Vietnamese government announced that there had been 20 breaches of the New Year's ceasefire resulting in nine South Vietnamese and 16 People's Army of Vietnam (PAVN)/Vietcong VC killed.
U.S. aircraft flew more than 200 sorties to attack PAVN supply lines in Cambodia and Laos.
The U.S. Army reported that between 1969 and 1971 over 700 Fraggings occurred resulting in 82 dead and 631 wounded.
2 January President Richard Nixon announced that unilateral U.S. troop withdrawals from South Vietnam would continue, but a residual force of 25–35,000 would remain until all U.S. prisoners of war (POWs) were released.
South Vietnam withdrew more than 10,000 soldiers from operations in Cambodia to bolster defenses around Saigon in preparation for an expected PAVN/VC during Tết.
3 January Democratic Senator George McGovern accused Nixon of deceiving the public by suggesting that the North Vietnamese had rejected a release of POWs in return for a firm date for withdrawal of U.S. forces, saying that Nixon was using the issue to justify bombing the North and propping up the government of President of South Vietnam Nguyễn Văn Thiệu.
Max Frankel writing in The New York Times stated that Nixon was buying time to build up South Vietnam through Vietnamization and improve the position of anti-communist forces in Cambodia and Laos.
PAVN ambushed a U.S. infantry patrol northeast of Saigon and then shot down three Medevac helicopters, resulting in one U.S. killed.
4 January A Royal Lao Army (RLA) spokesman said that a PAVN force, supported by two Vietnam People's Air Force (VPAF) MiG jets, had destroyed a bridge on Route 13, from the besieged RLA base at Long Tieng. Seven RLA and 14 PAVN were killed in the attack.
5 January A United States Air Force (USAF) F-105G escorting B-52 Stratofortresses on a bombing mission over Laos attacked a PAVN radar-guided antiaircraft gun north of the Ban Karai Pass in the first "protective reaction" strike of the year. B-52s also bombed PAVN positions near Khe Sanh.
The South Vietnamese Joint General Staff (JGS) announced that they were withdrawing from fixed bases in Cambodia and would in future rely on a 15,000 man airmobile and armored cavalry task force assigned to Military Region 3 to undertake operations there.
North Vietnam announced that in order for the U.S. to secure the release of its POWs it must "completely end the war of aggression in Vietnam and remove all its troops from Vietnam" and "completely end the Vietnamization policy of continuing the war" which it denounced as a "plot to withdraw United States forces but still continue the war of American aggression by puppet forces under United States direction and with United States support and supplies."
6 January At the Paris Peace Talks the North Vietnamese reiterated their position that U.S. POWs would only be released once the U.S. withdrew all its forces and the U.S. "give up aggression, stop the "Vietnamization" of the war, pull out from South Vietnam all the troops... stop backing the Nguyễn Văn Thiệu bellicose puppet group."
Democratic Senator Edmund Muskie called for the U.S. to withdraw from South Vietnam regardless of the consequences saying that 55,000 American lives and $130 billion spent on the war had been "wasted."
8 January In response to India's decision to upgrade its diplomatic relations with North Vietnam to ambassadorial level, South Vietnam announced that India could no longer be regarded as an impartial member of the International Control Commission and barred the new Indian chair of the commission from entering South Vietnam.
9 January A VC threw a grenade into a youth rally in Quy Nhon in an attempt to kill the Bình Định province chief, the grenade killed two teachers and seven students and wounded 110 others.
RLA forces held off PAVN attacks on Ban Nhik, the last government position on the Boloven Plateau, east of Pakse. In three days of fighting the RLA claimed to have killed more than 75 PAVN around Ban Nhik with a further 200 killed in airstrikes and reports of more than 200 wounded being taken to Paksong.
10 January The Cambodian Khmer National Army (ANK) withdrew from the town of Ponhea Kraek (Krek) near the Fishhook abandoning the last remaining road link between Cambodia and South Vietnam. Further south in the Parrot's Beak the South Vietnamese Army of the Republic of Vietnam (ARVN) began Operation Prek Ta against the PAVN in that area of Cambodia. The objective of the offensive was to disrupt the preparations of the North Vietnamese for an anticipated offensive on Tết, 15 February.Deac, Wilfed P. (1996), "Losing Ground to the Khmer Rouge", Vietnam Magazine, Dec 1996, http://www.historynet.com/losing-ground-to-the-khmer-rouge.htm , accessed 9 Jun 2015
Former Vice President Hubert Humphrey announced his candidacy for the Democratic presidential nomination and criticized the slow pace of withdrawal from South Vietnam, saying that if he had been elected in 1968 all U.S. forces would have been withdrawn already.
The New York Times reported on the growing expectation of a PAVN offensive in the Central Highlands timed to coincide with Nixon's visit to China.
Three Communist Party of Thailand sappers attempted to destroy B-52s at U-Tapao Royal Thai Navy Airfield, Thailand using grenades and satchel charges. One attacker was apparently killed in the attack, while the other two managed to cause minor damage to three B-52s before fleeing the base.
11 January The South Vietnamese military acknowledged that it was withdrawing its forces from Krek and other locations in Cambodia in preparation for an expected PAVN offensive during Tết.
The PAVN fired two SA-2 Surface-to-air missiles (SAMs) at a USAF F-4 Phantom near Tchepone, showing the continuous improvement of PAVN air defences in Laos. A USAF F-4 fired two missiles at a radar site in North Vietnam in a "protective reaction" strike while escorting B-52s in a bombing raid on the Ban Karai Pass.
RLA forces abandoned Ban Nhik after four days of heavy fighting.
12 January Le Duc Tho, Politburo member and secret negotiator for North Vietnam in the Paris Peace Talks, cabled the head of Central Office for South Vietnam (COSVN) in South Vietnam that "we and the enemy are preparing for a ferocious confrontation... during the upcoming spring and summer." In addition to supporting the PAVN troops in South Vietnam, Tho instructed COSVN to devote attention to attacking the Civil Operations and Revolutionary Development Support (CORDS) pacification program] and to the political struggle in the cities of South Vietnam.(FRUS) Foreign Relations of the United States, 1969-1976, Volume VIII, Vietnam, January–October 1972, Document 1, https://history.state.gov/historicaldocuments/frus1969-76v08/d1#fn3 , accessed 8 Jun 2015
The 2,400-man ANK 22nd Brigade deployed near Krek dissolved itself with officers and soldiers shedding their uniforms and fleeing into South Vietnam.
More than 34 PAVN/VC shelling and ground attacks were reported in the most intensive attacks in three months. A VC unit attacked a 30-man ARVN patrol in the Mekong Delta killing three, with eleven missing. The PAVN/VC shot down a U.S. UH-1 helicopter in the Mekong Delta killing all four crewmen.
Cambodian and South Vietnamese forces began a joint operation near Ang Tassom south of Phnom Penh.
13 January Nixon announced that 70,000 American troops would be pulled out of South Vietnam by 1 May, cutting the existing force of 139,000 by half.
PAVN/VC attacks continued throughout South Vietnam conducting 26 attacks resulting in 33 PAVN/VC killed and 15 ARVN killed. Two USAF F-105Gs fired missiles at a SAM site on the Laos-North Vietnam border, while escorting B-52s.
14 January A USAF F-105G destroyed a SAM site north of the Vietnamese Demilitarized Zone (DMZ) while escorting United States Navy fighter-bombers attacking the Ho Chi Minh Trail.
15 January Military Assistance Command, Vietnam (MACV) reported that the North Vietnamese were moving more SAMs closer to the DMZ with an F-105G destroying a SAM site in the eastern DMZ and two SA-2s being fired on an F-105 flying north of the DMZ near the Laos-North Vietnam border. In ongoing attacks throughout South Vietnam 89 PAVN/VC, 15 ARVN and 15 civilians were reported killed.
RLA forces were flown into Long Tieng and were reported to have broken the siege of the base, recapturing Skyline Ridge north of the base.
16 January Leaders of 46 Protestant, Catholic, and Jewish organizations met in Kansas City and asked for the withdrawal of American military personnel from South Vietnam and a cut-off in aid to the South Vietnamese government.
USAF jets engaged a VPAF MiG-21 jet over northern Laos for the first time in a year. A PAVN/VC mortar attack on Cam Ranh Base killed seven ARVN.
17 January In a secret letter to Thiệu, Nixon warned that his refusal to sign a peace agreement to end the war would make it impossible for the U.S. to continue support for South Vietnam.
U.S. aircraft flew more than 200 airstrikes against PAVN supply lines in Laos to disrupt preparations for a PAVN offensive and returned fire against PAVN SAM sites near the Ban Karai Pass.
18 January Seymour Hersh who wrote the first detailed account of the My Lai massacre reported that a U.S. Army investigation showed that more than 347 civilians had been killed at My Lai, rather than less than 200 as previously reported and that more than 90 civilians had been killed in the nearby village of My Khe 4 on the same day.
Two VPAF MiGs conducted an unsuccessful hit and run attack on USAF F-4s over northern Laos, firing three air-to-air missiles before fleeing back across the border. USAF aircraft conducted more than 250 airstrikes over Laos.
19 January A U.S. Navy F-4B piloted by Lieutenant Duke Cunningham and Lieutenant j.g. William P. Driscoll engaged and shot down a VPAF MiG-21 near Quang Lang Air Base scoring the first U.S. aerial victory in 22 months.
Reporters were flown into Long Tieng for the first time ever to view operations at the previously secret base.
A U.S. UH-1 helicopter was shot down southwest of Khe Sanh while attempting to rescue the crew of a shot-down F-4. Two crewmembers were killed and a further six injured.
20 January The head of MACV, General Creighton Abrams cabled Washington that "the enemy [North Vietnam] is preparing and positioning his forces for a major offensive.... There is no doubt this is to be a major campaign." Abrams requested additional authority to use U.S. American air power to mount an effective defense.
More than 10,000 ARVN began a sweep of PAVN/VC base areas in a plantation northwest of Saigon as part of ongoing efforts to disrupt an anticipated Tết offensive.