|Advisory||15 March 1962 - 7 March 1965|
|Defense||8 March 1965 - 24 December 1965|
|Counteroffensive||25 December 1965 - 30 June 1966|
|Counteroffensive, Phase II||1 July 1966 - 31 May 1967|
|Counteroffensive, Phase III||1 June 1967 - 29 January 1968|
|Tet Counteroffensive||30 January 1968- 1 April 1968|
|Counteroffensive, Phase IV||2 April 1968 - 30 June 1968|
|Counteroffensive, Phase V||1 July 1968- 1 November 1968|
|Counteroffensive, Phase VI||2 November 1968 - 22 February 1969|
|Tet 69/Counteroffensive||23 February 1969 - 8 June 1969|
|Summer-Fall 1969||9 June 1969 - 31 October 1969|
|Winter-Spring 1970||1 November 1969 - 30 April 1970|
|Sanctuary Counteroffensive||1 May 1970 - 30 June 1970|
|Counteroffensive, Phase VII||1 July 1970 - 30 June 1971|
|Consolidation I||1 July 1971 - 30 November 1971|
|Consolidation II||1 December 1971 - 29 March 1972|
|Cease-Fire||30 March 1972 - 28 January 1973|
Advisory, 15 March 1962 - 7 March 1965. During this period, direct U.S. involvement in the Vietnam conflict increased steadily as U.S. trained Vietnamese pilots moved Vietnamese helicopter units into and out of combat. Ultimately the United States hoped that a strong Vietnamese government would result in improved internal security and national defense. The number of U.S. advisors in the field rose from 746 in January 1962 to over 3,400 by June; the entire U.S. commitment by the end of the year was 11,000, which included 29 U.S. Army Special Forces detachments. These advisory and support elements operated under the Commander, U.S. Military Assistance Command, Vietnam, a position established 8 February 1962. The object of American military assistance was to counter the threat to the government of the Republic of Vietnam posed by the insurgency of an estimated 30,000 regular communist Viet Cong and civilian sympathizers among the population. Despite what appeared to be considerable successes in consolidating the population in a series of defended strategic hamlets, and in establishing local defense forces, the U.S. equipped Army of the Republic of Vietnam repeatedly demonstrated an unwillingness to close with the enemy. A corrupt government and bitterly contending Vietnamese political factions further hampered a coherent prosecution of the war with American advisors, who nevertheless continued their efforts well into the period of large scale commitments of U.S. Army forces to the conflict.
Defense, 8 March 1965 - 24 December 1965. During this campaign the U.S. objective was to hold off the enemy while gaining time needed to build base camps and logistical facilities. The U.S. also attempted to consolidate its ground operations more efficiently. For this purpose, it organized the U.S. Army Vietnam (USARV). U.S. support in the I Corps tactical zone, composed of five northernmost provinces, was to be primarily a Marine Corps responsibility; the U.S. Army was to operate mainly in the II and III Corps tactical zones which comprised the Central highlands, adjacent coastal regions, and the area around Saigon; and ARVN troops were to retain primary responsibility for the Delta region of the IV Corps.
On 19 October 1965. three VC regiments totaling 6,000 men attacked a Civil Irregular Defense Group (CIDG) - U.S. Special Forces at Plei Me, near the entrance to the Ia Drang Valley, in what purported to be the start of a thrust to cut the country in half.
With the assistance of massive air strikes, elements of the newly arrived 1st Cavalry Division thwarted the enemy in a battle that lasted nearly a month and included several engagements. The Ia Drang Valley action was the costliest in terms of casualties to date. The successful defense of the region improved security in and around the Central Highlands and raised the morale of the soldiers involved.
Counteroffensive, 25 December 1965 - 30 June 1966. Following the U.S. victory in the Ia Drang Valley, American forces for the remainder of 1965 and well into 1966 sought to keep the enemy off balance while building base camps and logistical installations. This involved search and destroy operations to protect the logistical bases under construction along the coast and the base camps for incoming U.S. units in the provinces near Saigon.
Also of particular concern to the American military mission was the protection of the government and the people of South Vietnam. To accomplish the tasks outlined U.S. efforts were concentrated in the most vital and heavily populated regions. The III Marine Amphibious Force supported the South Vietnamese I Corps in the northern provinces; the I Field Force supported the Vietnamese II Corps in the central region; and the II Field Force supported the South Vietnamese III Corps around Saigon. Consequently, the major battles of the year occurred in these critical areas. The 1st Brigade, 101st Airborne Division, the Korean 2d Marine Brigade, and the ARVN 47th Regiment began Operation VAN BUREN on 19 January to locate and destroy the North Vietnamese 95th Regiment, which was believed to be in the Tuy Hoa Valley. Their mission included protecting the rice harvest produced in the coastal region. The successful execution of these assignments resulted in serious enemy losses. During 20-23 January, a temporary cease fire was proclaimed in honor of the lunar new year (Tet), although minor clashes continued throughout this period.
During February and March, U.S. intelligence reported heavy North Vietnamese Army infiltration from Laos and across the demilitarized zone into Quang Tri Province. Only the South Vietnamese 1st Division and a single U.S. marine battalion were deployed to the province. However, to defend against this threatened invasion the bulk of the U.S. 3d Marine Division and the first U.S. Army combat units, the 173d Airborne Brigade, were moved into the northern provinces. On April 12, U.S. B-52s based on Guam bombed infiltration routes near the Laos border in the first use of these weapons against NVA. Throughout this phase of the campaign, the enemy continued to take refuge in Laos, Cambodia, and North Vietnam. Driving the enemy back removed the threat of harassment of the populace by North Vietnamese regular forces and curbed local guerrilla activity.
Counteroffensive, Phase II, 1 July 1966 - 31 May 1967. United States operations after 1 July 1966 were a continuation of the earlier counteroffensive campaign. Recognizing the interdependence of political, economic, sociological, and military factors, the Joint Chiefs of Staff declared that American military objectives should be to cause North Vietnam to cease its control and support of the insurgency in South Vietnam and Laos, to assist South Vietnam in defeating Viet Cong and North Vietnamese forces in South Vietnam, and to assist South Vietnam in pacification extending governmental control over its territory.
North Vietnam continued to build its own forces inside South Vietnam. At first this was done by continued infiltration by sea and along the Ho Chi Minh trail and then, in early 1966, through the Demilitarized Zone (DMZ). U.S. air elements received permission to conduct reconnaissance bombing raids, and tactical air strikes into North Vietnam just north of the DMZ, but ground forces were denied authority to conduct reconnaissance patrols in the northern portion of the DMZ and inside North Vietnam. Confined to South Vietnamese territory U.S. ground forces fought a war of attrition against the enemy, relying for a time on body counts as one standard indicator for measuring successful progress for winning the war.
During 1966 there were eighteen major operations, the most successful of these being Operation WHITE WING (MASHER). During this operation, the 1st Cavalry Division, Korean units, and ARVN forces cleared the northern half of Binh Dinh Province on the central coast. In the process they decimated a division, later designated the North Vietnamese 3d Division. The U.S. 3d Marine Division was moved into the area of the two northern provinces and in concert with South Vietnamese Army and other Marine Corps units, conducted Operation HASTINGS against enemy infiltrators across the DMZ.
The largest sweep of 1966 took place northwest of Saigon in Operation ATTLEBORO, involving 22,000 American and South Vietnamese troops pitted against the VC 9th Division and a NVA regiment. The Allies defeated the enemy and, in what became a frequent occurrence, forced him back to his havens in Cambodia or Laos.
By 31 December 1966, U.S. military personnel in South Vietnam numbered 385,300. Enemy forces also increased substantially, so that for the same period, total enemy strength was in excess of 282,000 in addition to an estimated 80,000 political cadres. By 30 June 1967, total U.S. forces in SVN had risen to 448,800, but enemy strength had increased as well.
On 8 January U.S. and South Vietnamese troops launched separate drives against two major VC strongholds in South Vietnam-in the so-called "Iron Triangle" about 25 miles northwest of Saigon. For years this area had been under development as a VC logistics base and headquarters to control enemy activity in and around Saigon. The Allies captured huge caches of rice and other foodstuffs, destroyed a mammoth system of tunnels, and seized documents of considerable intelligence value.
In February, the same U.S. forces that had cleared the "Iron Triangle", were committed with other units in the largest allied operation of the war to date, JUNCTION CITY. Over 22 U.S. and four ARVN battalions engaged the enemy, killing 2,728. After clearing this area, the Allies constructed three airfields; erected a bridge and fortified two camps in which CIDG garrisons remained as the other allied forces withdrew.
Counteroffensive, Phase III, 1 June 1967-29 January 1968. The conflict in South Vietnam remains basically unchanged. As Operation JUNCTION CITY ended, elements of the U.S. 1st and 25th Infantry Divisions, the 11th Armored Cavalry Regiment, and the forces of the Army of the Republic of Vietnam swung back toward Saigon to conduct another clearing operation, MANHATTAN. This took peace in the Long Nguyen base area just north of the previously cleared "Iron Triangle."
South Vietnamese Armed Forces became more active and capable under U.S. advisors. During the year the Vietnamese Special Forces assumed responsibility for several Special Forces camps and for the CIDG companies manning them. In each case all of the U.S. advisors withdrew, leaving the Vietnamese in full command.
With an increased delegation of responsibility to them, the South Vietnamese conducted major operations during 1967, and, in spite of VC attempts to avoid battle, achieved a number of contacts.
Despite the success of U.S. and South Vietnamese Army operations, there were indications in the fall of 1967 of another enemy build-up, particularly in areas close to Laos and Cambodia. In late October, the VC struck again at the Special Forces Camp at Loc Ninh. Fortunately Vietnamese reinforcements saved the camp. At the same time, approximately 12,000 VC troops converged on a Special Forces camp at Dak To. This camp was located in northern Kontum Province, where the borders of Laos, Cambodia, and South Vietnam meet. In response to this potential threat, the U.S. and South Vietnam committed a total of sixteen battalions to the region to counter a disturbing enemy resurgence at Kontum and Loc Ninh.
Tet Counteroffensive, 30 January 1968-1 April 1968. On 29 January 1968 the Allies began the Tet-lunar new year expecting the usual 36-hour peaceful holiday truce. Because of the threat of a large-scale attack and communist buildup around Khe Sanh, the cease fire order was issued in all areas over which the Allies were responsible with the exception of the I CTZ, south of the Demilitarized Zone.
Determined enemy assaults began in the northern and Central provinces before daylight on 30 January and in Saigon and the Mekong Delta regions that night. Some 84,000 VC and North Vietnamese attacked or fired upon 36 of 44 provincial capitals, 5 of 6 autonomous cities, 64 of 242 district capitals and 50 hamlets. In addition, the enemy raided a number of military installations including almost every airfield. The actual fighting lasted three days; however Saigon and Hue were under more intense and sustained attack.
The attack in Saigon began with a sapper assault against the U.S. Embassy. Other assaults were directed against the Presidential Palace, the compound of the Vietnamese Joint General Staff, and nearby Ton San Nhut air base.
At Hue, eight enemy battalions infiltrated the city and fought the three U.S. Marine Corps, three U.S. Army and eleven South Vietnamese battalions defending it. The fight to expel the enemy lasted a month. American and South Vietnamese units lost over 500 killed, while VC and North Vietnamese battle deaths may have been somewhere between 4,000 and 5,000.
Heavy fighting also occurred in two remote regions: around the Special Forces camp at Dak To in the central highlands and around the U.S. Marines Corps base at Khe Sanh. In both areas, the allies defeated attempts to dislodge them. Finally, with the arrival of more U.S. Army troops under the new XXIV Corps headquarters to reinforce the marines in the northern province, Khe Sanh was abandoned.
Tet proved a major military defeat for the communists. It had failed to spawn either an uprising or appreciable support among the South Vietnamese. On the other hand, the U.S. public became discouraged and support for the war was seriously eroded. U.S. strength in South Vietnam totaled more than 500,000 by early 1968. In addition, there were 61,000 other allied troops and 600,000 South Vietnamese.
The Tet Offensive also dealt a visibly severe setback to the pacification program, as a result of the intense fighting needed to root out VC elements that clung to fortified positions inside the towns. For example, in the densely populated delta there had been approximately 14,000 refugees in January; after Tet some 170,000 were homeless. The requirement to assist these persons seriously inhibited national recovery efforts.
Counteroffensive. Phase IV, 2 Apri1 1968-30 June 1968. During this period friendly forces conducted a number of battalion-size attritional operations against the enemy.
Operations PEGASUS-Lam Son 207 relieved the Khe Sanh Combat Base on 5 April and thereby opened Route 9 for the first time since August 1967. This operation not only severely restricted the North Vietnamese Army's use of western Quang Tri Province but also inflicted casualties on the remnants of two North Vietnamese divisions withdrawing from the area. This success was followed by a singular allied spoiling operation in the A Shau Valley, Operation DELAWARE-Lam Son. These two operations prevented the enemy from further attacking I Corps Tactical Zone population centers and forced him to shift his pressure to the III Corps Tactical Zone.
During the period 5-12 May 1968 the Viet Cong launched an offensive with Saigon as the primary objective. Friendly forces defended the city with great determination. Consequently Saigon was never in danger of being overrun. Small Viet Cong units that did manage to get into the outskirts were fragmented and driven out with great loss of enemy life. By the end of June 1968 friendly forces had decisively blunted the enemy's attacks, inflicted very heavy casualties, and hindered his ability to attack urban areas throughout the Republic of Vietnam. The enemy was forced to withdraw to his sanctuaries.
The strength of the U.S. Army in Vietnam reach a peak of nearly 360,000 men during this period.
Counteroffensive, Phase V, 1 July 1968 - 1 November 1968. During this period a country-wide effort was begun to restore government control of territory lost to the enemy since the Tet offensive. The enemy attempted another such offensive on 17-18 August but his efforts were comparatively feeble and were quickly overwhelmed by Allied forces.
In the fall of 1968 the South Vietnamese government, with major U.S. support, launched an accelerated pacification campaign. All friendly forces were coordinated and brought to bear on the enemy in every tactical area of operation. In these intensified operations, friendly units first secured a target area, then Vietnamese government units, regional forces/popular forces, police and civil authorities screened the inhabitants, seeking members of the Viet Cong infrastructure. This technique was so successful against the political apparatus that it became the basis for subsequent friendly operations. Government influence expanded into areas of the countryside previously dominated by the Viet Cong to such an extent that two years later at least some measure of government control was evident in all but a few remote regions.
Counteroffensive, Phase VI, 2 November 1968 - 22 February 1969. In November 1968 the South Vietnam government with American support began a concentrated effort to expand security in the countryside. This project was known as the "Accelerated Pacification Campaign."
This period covers the election of President Richard M. Nixon and a change of policy brought about by his administration after January 1969 when he announced a coming end to US combat in Southeast Asia and a simultaneous strengthening of South Vietnam's ability to defend itself. Formal truce negotiations began in Paris on January 25, 1969. The period can be characterized as marking time in preparation for an about face. Forty-seven ground combat operations were recorded during this period, the following being the most important:
- Operation NAPOLEON in the Dong Ha area initiated previously (1967) by Marine units, terminated on 9 December 1968.
- Operation WHEELER WALLOWA by 3d Brigade, 1st Cavalry Division and 196th Infantry Brigade (Light) in north-central Quan Tin Province. This ended on 11 November.
- Operation MACARTHUR initiated by 4th U.S. Infantry Division in II Corps tactical zone terminated on 31 January 1969.
- Operation COCHISE GREEN conducted by the 173d Airborne Brigade in Binh Dinh Province.
- Operation TOAN THANG II consisted of ground operations throughout III CTZ. This was a multi-division operation involving allied forces.
- Operation SEA LORDS was a coast and riverine operation. On 6 December Operation GIANT SLINGSHOT was started to disrupt enemy infiltration of materials from the "Parrot's Beak" area of Cambodia. Air operations continued to be important with over 60,000 sorties flown.
Tet 69/Counteroffensive, 23 February 1969 - 8 June 1969. From Tet 1969 through the month of June, the enemy again tried to sustain an offensive. His inability to do so can be largely attributed to aggressive allied ground operations. Between 23 February and 8 June 1969, a total of 70 significant named ground operations were terminated resulting in heavy enemy loss of life and materiel. The main operations concluded during this period were:
- The 3d Marine Division's Operation KENTUCKY aimed at preventing enemy infiltration through the Demilitarized Zone in central Quang Tri Province. Throughout the early part of January 1969, Viet Cong/North Vietnamese Army forces continued to avoid major contacts with Free World Forces. Their continual movement to avoid friendly forces or to search for food and supplies contributed to a decrease in the enemy-initiated ground attacks and attacks-by-fire in Quang Tri Province.
- Operation NEVADA EAG:E, initiated on 17 May 1968 in Thua Thien Province, continued in 1969 as the U.S. 101st Airborne Division continued to defeat enemy personnel, and capture rice caches, material, and installations within its large area of operations, where it undertook offensive sweeps along Route 547 and around Song Bo.
- Two battalions of the 4th Marine Regiment were engaged in Operation SCOTLAND II. Initiated on 15 April 1968, this multi-battalion search and clear operation was centered in and around Khe Sanh.
- The IV Corps Tactical Zone Dry Weather Campaign began on 1 December 1968 in support of the overall mission to prevent Viet Cong units from interfering with pacification efforts. This operation, "Speedy Express," interdicted lines of enemy communication and denied him the use of base areas. In 1969 the 1st Brigade, 9th U.S. Infantry Division continued the operation in Dinh Tuong Province, using its highly successful night ambush tactics while the 2d Brigade continued its mission with the Mobile Riverine Force. Although engagements in Operation SPEEDY EXPRESS were typically small, the 9th Infantry Division fought several sizeable engagements with impressive results.
On 23 February U.S. Navy units and installations at Da Nang, Tan An, Ben Luc, Go Dan Ha, and Tra Cu came under numerous and widespread attacks associated with a new enemy offensive, but since many units in these areas were poised to meet these attacks they caused only minimal damage. April saw the heaviest cumulative enemy activity in the barrier interdiction camapign to date.
Summer-Fall 1969, 9 June 1969-31 October 1969. During the summer and fall of 1969, conduct of operations was increasingly turned over to Vietnamese, US troops withdrew in greater numbers amid reaffirmations of support for the Republic of South Vietnam government. President Nixon announced the reduction of the U.S. military presence in South Vietnam which would be demonstrated initially by the withdrawal of 25,000 troops by 31 August 1969.
American troop strength had peaked at 543,400 in April 1969 but dropped to 505,500 by mid October. More scattered than before, enemy attacks were concentrated on South Vietnamese positions. U.S. combat deaths were down in the early fall as American units switched to small unit actions. The trend was not constant, however, because U.S. troops deaths which had fallen well below l00 a week in the fall, rose above 100 later in the year.
Winter-Spring 1970, 1 November 1969-30 April 1970. An increase in enemy-initiated attacks, at the highest level since 4-5 September signaled the start of the first phase of the Communist winter campaign. This was highlighted by intensified harassment incidents, and attacks throughout the Republic of Vietnam. In November-December these were heaviest in Corps Tactical Zones III and IV (around Saigon), primarily directed against Vietnamese military installations in order to disrupt the pacification program. The most significant enemy activity occurred in November with heavy attacks upon By Prang and Duc Lap in CTZ II (Central Vietnam).
By February 1970 the focus of enemy activity began to shift to CTZ I and II. Attacks increased steadily, reaching a peak in April 1970. Hostile forces staged their heaviest attacks in the Central Highlands near Civilian Irregular Defense Group camps at Dak Seang, Dak Pek, and Ben Het in I CTZ. The enemy also conducted numerous attacks by fire and several sapper attacks against U.S. fire support bases. This high level of enemy activity began in I CTZ in April and continued through May.
During the period 1 November 1969 through 30 April 1970 U.S. and allied forces concentrated on aggressive operations to find and destroy enemy main and local forces, the penetration of base camps and installations and the seizure of enemy supplies and materiel. These operations sought to deny the enemy the initiative and to inflict heavy losses in men and materiel. Further progress was made in Vietnamization through improving the Republic of Vietnam Armed Forces. As a result of these advances three brigades of the 1st U.S. Infantry Division and several major U.S.M.C. units were withdrawn from Vietnam during this period.
The enemy made several efforts to take the offensive at Dak Seang, which was attacked on 1 April 1970 and remained under siege throughout the month, and at Quang Duc in the By Prong-Duc Lap area which ended on 28 December. Only Vietnamese forces were engaged in both of these operations, the Quang Duc campaign involving some 12,000 ARVN troops. South Vietnamese forces again took the offensive on 14 April in a bold 3-day operation in the Angel's Wing area along the Cambodian border. The Vietnamese Army completed this mission in an aggressive professional manner without U.S. support-further evidence of their growing proficiency.
Sanctuary Counteroffensive, 1 May 1970 - 30 June 1970. This campaign was mainly concerned with the Allied incursion into Cambodia, codenamed Operation ROCK CRUSHER. As American withdrawal from South Vietnam proceeded, increasing concern arose over the enemy's strength in the sanctuaries inside Cambodia. With the emergence in Cambodia of an antiCommunist government under Lon Nol, President Nixon relaxed the restrictions on moving against the bases inside Cambodia. Meanwhile, the North Vietnamese and Viet Cong began to move on the Cambodian capital of Phnom Penh. At this juncture Lon Nol appealed to the United States for help. American and allied Vietnamese forces began large-scale offensives in Cambodia on 1 May. Eight major US Army and South Vietnamese operations took place in Cambodia in May and June with the object of cutting enemy communication lines, seizing the sanctuary areas and capturing the shadowy Central Office for South Vietnam (COSVN) described as the control center for enemy military operations against III CTZ.
Counteroffensive, Phase VII, 1 July 1970 - 30 June 1971. Fighting continued in Cambodia during early February before and after South Vietnam began its U.S.-aided drive in Laos, Lam Son 719, the most significant operation during this campaign.
Lam Son 719 was conducted out of I Corps by Vietnamese troops with US fire and air support. Their object was to cut the Ho Chi Minh Trail and to destroy enemy bases at Techepone, Laos. The operation consisted of four phases. In Phases I, called Operation DEWEY CANYON II, the 1st Brigade, US 5th Infantry Division (Mechanized) occupied the Khe Sanh area and cleared Route No. 9 up to the Laotian border. In the meantime, the US 101st Airborne Division conducted diversionary operations in the A Shau Valley. The US 45th Engineer Group had the mission of repairing Route No. 9 up to the Laotian border. This lasted from 30 January to 7 February 1971. During Phase II US forces continued to provide fire support, helilift, and tactical and strategic air support for ARVN units. This phase was 8 February to March 1971. Phase III ran from March to 16 March 1971; Phase IV was the withdrawal phase.
Faced with mounting losses, Lt. Gen. Hoang Xuan Lam, the commander of the invasion forces, decided to cut short the operation and ordered a withdrawal.
Lam Son 719, though it was less than a signal success, forestalled a Communist offensive in the spring of 1971. Enemy units and replacements enroute south were diverted to the scene of the action.
Consolidation I, 1 July 1971 - 30 November 1971. This period witnessed additional progress in the Vietnamization program which included turning over the ground war to South Vietnam, sustaining the withdrawal of U.S. troops, but also continuing, U.S. air strikes on enemy targets.
South Vietnam assumed full control of defense for the area immediately below the demilitarized zone on 11 July, a process begun in 1969. Secretary of Defense Melvin R. Laird announced completion of Phase I of Vietnamization on 11 August which meant that the U.S. relinquished all ground combat responsibilities to the Republic of Vietnam. The participation of U.S. forces in ground combat operations had not ceased, however, U.S. maneuver battalions were still conducting missions, and the 101st Airborne Division joined the 1st Army of Vietnam 1st Infantry Division in Operation JEFFERSON GLEN that took place in Thua Thien Province in October. This was the last major combat operation in Vietnam which involved U.S. ground forces. Following the close of Operation JEFFERSON GLEN on 8 October, the 101st began stand-down procedures and was the last U.S. division to leave Vietnam.
U.S. troop strengths decreased during Consolidation I. American battle deaths for July 1971 were 66, the lowest monthly figure since May 1967. By early November, U.S. troop totals dropped to 191,000, the lowest level since December 1965. In early November, President Nixon announced that American troops had reverted to a defensive role in Vietnam.
Consolidation II, 1 December 1971 - 29 March 1972. The U.S. continued to reduce its ground presence in South Vietnam during late 1971 and early 1972, but American air attacks increased while both sides exchanged peace proposals.
In early January 1972 President Nixon confirmed that U.S. troop withdrawals would continue but promised that a force of 25,000-30,000 would remain in Vietnam until all American prisoners of war were released. Secretary of Defense Laird reported that Vietnamization was progressing well and that U.S. troops would not be reintroduced into Vietnam even in a military emergency. U.S. troop strength in Vietnam dropped to 136,500 by 31 January 1972, to 119,600 by 29 February, and then to 95,500 by the end of March.
During the last week of December 1971 U.S. Air Force and Navy planes carried out 1,000 strikes on North Vietnam, the heaviest U.S. air attacks since November 1968. Allied commanders insisted that it was necessary because of a huge buildup of military supplies in North Vietnam for possible offensive operations against South Vietnam and Cambodia. Stepped up North Vietnamese anti-aircraft and missile attacks on U.S. aircraft that bombed the Ho Chi Minh Trail in Laos also contributed to the decision. During January 1972 American planes maintained their intermittent bombardment of missile sites in North Vietnam and on he Laotian border and also struck North Vietnamese troop concentrations in the Central Highlands of South Vietnam.
On 25 January President Nixon announced an eight part program to end the war which included agreement to remove all U.S. and foreign allied troops from Vietnam no later than six months after a peace agreement was reached. The North Vietnamese and Viet Cong delegates rejected the proposal and insisted upon complete withdrawal of all foreign troops from Indochina and cessation of all forms of U.S. aid to South Vietnam.
Cease-Fire, 30 March 1972 - 28 January 1973. On 30 March 1972 the North Vietnamese Army launched its greatest offensive of the entire war. The enemy deployed the greatest array of troops and modern weapons to date in a major effort to end the war with conventional forces and seized considerable territory in an effort to exercise control of key provinces throughout Vietnam.
During this critical period the Vietnamization program continued in the face of the North Vietnamese invasion and the successful counterattack by the armed forces of the Republic of Vietnam. Army aviation units played an impressive role throughout the period, flying reconnaissance, close support missions, and transporting troops. As U.S. combat troops were withdrawn from Vietnam, the role of helicopter units increased in importance and they responded to the challenge of continuing to support while preparing the RVNAF to assume their function. Similarly, advisors of all services contributed immeasurably to the defeat of the enemy invasion and the continued Vietnamization process. Army and Marine advisors fought side-by-side with their RVNAF counterparts to stop and defeat the enemy invasion, as the Vietnamese counteroffensive gained momentum and the reduction of field advisers continued. The advisory effort shifted to emphasize training and to assure that the VNAF attained self-sufficiency prior to the complete withdrawal of the U.S forces.
Recapture of Quang Tri City on 16 September 1972 marked the complete failure of the enemy to hold any of the targeted provincial capitols. Massive aid replaced materiel lost during the spring counteroffensive. Retraining and reconstruction of selected RVNAF units increased their capabilities. The completion of the massive logistical buildup of RVNAF was accomplished, which enabled the RVNAF to become more self-sufficient as direct U.S. participation diminished. The US ground role in Vietnam was totally replaced by the RVNAF. During December 1972 and January 1973 the RVIVAF flew more than 45% of air sorties within Vietnam. In November 1972, the RVNAF began a C-130 training program and by January 1973 realized a significant increase in their capability. RVNAF forward air controllers began directing USAF and RVNAF strike aircraft in January 1973. The US policy of Vietnamization continued.
US combat and combat support operations were conducted in support of RVNAF ground operations during the North Vietnamese invasion and the counteroffensive including intensive interdiction of enemy supply routes into Vietnam. Since US ground forces had been reduced to seven battalions, the US ground combat role was limited to defense of key installations. Further reduction in troop ceilings led to the redeployment of all US ground combat battalions, leaving an Army contingent of combat support and service support units.