The War of the Flags (also known as Landgrab '73) was a phase of fighting throughout South Vietnam lasting from 23 January to 3 February 1973 as the forces of North and South Vietnam each sought to maximize the territory under their control before the ceasefire in place agreed by the Paris Peace Accords came into effect at 8:00 on 28 January 1973 (local time). The fighting continued past the ceasefire date and into early February. South Vietnamese forces made greater territorial gains and inflicted significant losses on the North Vietnamese forces.
Background At the end of the Easter Offensive in October 1972 both the Army of the Republic of Vietnam (ARVN) and the People's Army of Vietnam (PAVN) had suffered severe losses and were exhausted. The PAVN had gained permanent control of large areas of the four northernmost provinces – Quảng Trị, Thừa Thiên, Quảng Nam and Quảng Tín – and the western fringes of the II and III Corps sectors, totalling around 10% of South Vietnam.
The Paris Peace Talks resumed in October 1972 and the outline of the peace agreement was announced on 26 October 1972. One of the sticking points in the negotiations was North Vietnam's insistence that there should be a ceasefire in place, with the PAVN and Vietcong (VC) retaining control of the areas they occupied. South Vietnamese president Nguyễn Văn Thiệu opposed the continued PAVN occupation, but was coerced by the Nixon Administration to agree to this condition. The final terms of the peace accords were agreed by the parties on 23 January 1973, with signing to take place on 27 January and a country-wide ceasefire in place coming into effect on at 24:00 GMT on 27 January. A joint military commission of South Vietnamese and VC representatives established under the terms of the accords would determine the areas controlled by each side, which was replaced by the International Commission of Control and Supervision (ICCS), composed of representatives from Canada, Indonesia, Hungary and Poland.
MACV and South Vietnamese intelligence learned that the PAVN/VC planned general attacks throughout South Vietnam to take place immediately before the expected date of the ceasefire so as to maximize the areas under their control in the expectation that the ICCS monitors would be in place around the country and able to confirm PAVN/VC control and so forestall any South Vietnamese counterattacks. The ARVN prepared for these attacks and planned attacks of its own to regain ground ahead of the ceasefire. The US continued to support the South Vietnamese, principally with air strikes, until the ceasefire came into effect.
Battle I Corps
By late October 1972 the ARVN had recaptured Quảng Trị and held a line along the Thạch Hãn River. An attempt to advance to the south bank of the Cam Lộ/Cửa Việt River was repulsed in November. On 15 January 1973 the South Vietnamese Joint General Staff began planning began for a final assault by South Vietnamese Marines and ARVN to capture the south bank of the Cam Lộ/Cửa Việt River and the Cửa Việt Base. The attack was launched on the morning of 26 January and by 07:00 on 28 January the South Vietnamese had recaptured the base. At 08:00 Indochina Time on 28 January the ceasefire came into effect and US support for the operation ceased. On the evening of 29 January the PAVN counterattacked and by 31 January had recaptured the base. South Vietnamese losses were 40 killed and they claim to have inflicted over 1000 PAVN casualties.
South and west of Quảng Trị the PAVN B5 Front forces prevented any expansion of the ARVN Airborne Division's positions into the hills south of the Thạch Hãn River and against the Thạch Hãn River line itself. The PAVN built up their defenses in the highlands north of the Thạch Hãn River and west of Quảng Trị. Elements of the PAVN 304th Division were shifted to this sector, and additional antiaircraft units were brought into the B5 Front, so that by the end of January elements of at least 11 antiaircraft regiments were deployed in northwestern Quảng Trị Province. In late January 1973 elements of the PAVN 263rd SAM Regiment, equipped with SA-2 missiles, deployed to the former Khe Sanh Combat Base. The regiment had four firing battalions, each equipped with four to six launchers and one support battalion. The regiment was apparently deployed to protect the PAVN logistics hub of the Ho Chi Minh Trail, the A Sầu Valley and Route 9.
Further south in Thừa Thiên Province, on 24 January elements of the 803rd Regiment, 324B Division moved into the lowlands south of Camp Evans and north of Huế. On 25 January artillery and ground attacks began against ARVN positions around Huế. Between 27 January and 3 February elements of the 803rd Regiment attempted to interdict Highway 1 in the vicinity of the An Lo bridge. The PAVN captured a number of hamlets before being ejected by ARVN forces, losing over 200 killed. South of Huế, the PAVN 5th and 6th Regiments attacked the lowlands around Phu Bai Combat Base, gaining temporary control of several hamlets before being ejected and losing 175 killed.
In the PAVN's Military Region 5 which was responsible for Quảng Nam, Quảng Tín and Quảng Ngãi Provinces both the PAVN and VC overextended themselves and could not secure their gains. Intelligence sources revealed that the PAVN expected its main forces to be able to contain the ARVN in its bases and thereby permit local forces to invest the hamlets and villages.
In Quảng Nam Province, Front-4 had completed its preparations for the attacks by 22 January, including having the 575th Artillery Battalion move rockets into four firing positions for attacks against Da Nang. Fighting began on the morning of 26 January with a ground attack against Duc Duc and a rocket attack against Da Nang. Numerous attacks by fire and infantry assault were simultaneously conducted against ARVN positions and lines of communication throughout the province, and all district headquarters in Quảng Nam Province were hit. Da Nang received rocket attacks for three consecutive days. The PAVN supported the VC infiltrating the hamlets and villages and VC flags were observed in the hamlets of western Hieu Due District, southern and western Đại Lộc District, Điện Bàn District, northeastern Duc Duc, western Duy Xuyên District and parts of northern Quế Sơn District. Subsequent ARVN operations recovered some of these outlying villages and hamlets; the final result probably correctly reflected the relative military balance and political influence in the area.
In Quảng Tín Province the PAVN 711th Division was committed to defending its important base area in the Hiệp Đức District and played no offensive role. On 27 December the ARVN 3rd Division launched a spoiling attack against the Hiệp Đức base. Deep penetrations were made in the first few days and the I Corps Commander, Lt. Gen. Ngô Quang Trưởng, sought to exploit the early success by detaching the 51st Infantry Regiment from the 1st Division and on 3 January sent it to reinforce the 3rd Division. On 16 January the 3rd Division commander Maj. Gen. Nguyen Duy Hinh, committed the 51st Regiment to continue the attack to seize the former Firebase West on Hill 1460 () guarding the eastern approach to Hiệp Đức. The 51st was able to advance only part way up Hill 1460 and could not dislodge the PAVN infantry holding the crest. Meanwhile, elements of the 3rd Division's 2nd Regiment were across the Quế Sơn Valley and had seized the hill above Chau Son, thus controlling Route 534 into Hiệp Đức. On 24 January, the 3rd Division's attack continued, the objective was the former Firebase O'Connor () on high ground just east of Hiệp Đức. On 26 January, with the ceasefire imminent and VC forces moving into the populated lowlands of Quảng Nam, the 3rd Division had to terminate its attack. A strong counterattack by the 711th Division forces still on Firebase West prevented the 3d Division's infantry from gaining Firebase O'Connor, but the heavy casualties sustained by the 71lth demoralized and weakened it severely. By the end of January, 3rd Division troops were busy clearing VC forces from the hamlets west and southwest of Da Nang, and by the end of the month only one hamlet remained under PAVN/VC influence in Đại Lộc District.
In Quảng Ngai Province between 23 and 26 January VC forces infiltrated into assembly areas in the lowlands and on 27 January attacked throughout the lowlands, rocketing the provincial and district capitals, interdicting Highway 1 and overrunning several Regional Force and Popular Force outposts. In southern Quảng Ngai, the PAVN 52nd Regiment, 2nd Division, established defenses around the district town of Ba Tơ, which it had controlled since the fall of 1972. Rather than challenge this position, the ARVN deployed to prevent the 52nd Regiment from moving toward the lowlands. Holding its 1st Regiment in reserve, the PAVN 2nd Division used one battalion to support VC forces in Mộ Đức District, kept one battalion in the base area, and deployed the third to support the attack of the 141st Regiment in Duc Tho District. On 27 January the 141st Regiment, supported by two battalions of the PAVN 12th Regiment, 3rd Division reached Highway 1 south of Duc Tho and secured the rest of the district south to the border of Bình Định Province, including Sa Huỳnh Base, in which two battalions of the PAVN 12th Regiment, 3rd Division, supported the attack of the 2nd Division. Since the PAVN had blocked the only north - south line of communication and had secured a seaport, however small and undeveloped, in the center of the country, the South Vietnamese could hardly permit this situation to go unchallenged. Vigorous counterattacks succeeded in driving the PAVN from Sa Huỳnh by 16 February. PAVN losses were estimated to be in excess of 600 killed. Despite having seized Sa Huỳnh only the day before the ceasefire, the PAVN were outraged at being ejected from lands they "legitimately" occupied at the moment of ceasefire.
II Corps The southern part of PAVN Military Region 5 included Bình Định, Phú Yên and Khánh Hòa Provinces. South Vietnamese intelligence determined that the PAVN's objectives were to isolate the northern districts of Bình Định, hold the ARVN 22nd Division in its bases, cut Highway 1 and gain control of as much land and as many people as possible. From the PAVN viewpoint the prospects for success seemed good, for large segments of the population in the coastal areas of Bình Định and Phú Yên had long been sympathetic to the VC, and the ARVN 22nd Division had yet to establish any reputation for excellence in battle. Since the area along Highway 1 was fairly densely populated, it would provide a significant population base.