NESA Practice (NESA)-style practice: Account for the collapse of South Vietnam in 1975.

Needs a clear thesis, dated evidence, and integration of military and political factors. **Thesis.** South Vietnam collapsed in 1975 because the Paris Peace Accords left PAVN forces in the south, US aid was cut to a fraction of what was promised, the Thieu regime made strategic blunders in March 1975, and the PAVN final offensive was better resourced and better commanded than ARVN could resist. **The setup.** PAVN built up around 200,000 troops in the south under the 1973 ceasefire. Congress cut US aid to Saigon to $700 million for FY1975. ARVN faced fuel rationing and grounded aircraft. Nixon resigned 9 August 1974; the secret pledge to enforce the Accords was impossible to keep. **Phuoc Long.** PAVN took Phuoc Long Province in January 1975, the first whole province lost since 1965. The Ford administration's failure to respond signalled the US guarantee was dead. **Central Highlands.** Campaign 275 took Ban Me Thuot on 11 March 1975. Thieu ordered an evacuation on 14 March. "The convoy of tears" down Route 7B saw around 60,000 troops and 400,000 civilians flee with catastrophic losses. **Northern collapse.** Hue fell on 25 March, Da Nang on 29 March 1975. Around half of ARVN ceased to exist by the end of March. **Final offensive.** Xuan Loc fell on 20 April after the 18th Division's stand. Thieu resigned 21 April. Operation Frequent Wind evacuated around 7,000 people from 29 April. PAVN tank 843 crashed through the Presidential Palace gates at 1130 on 30 April 1975. **Reunification.** The Socialist Republic of Vietnam was proclaimed on 2 July 1976. Markers reward the 30 April 1975 date, the convoy of tears, and Frequent Wind.

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How and why did South Vietnam fall in 1975?

The collapse of South Vietnam in 1975, including the failure of the Paris Peace Accords, the final offensive of the People's Army of Vietnam, the fall of Saigon on 30 April 1975, and the reunification of Vietnam

Answer to the HSC Modern History Indochina dot point on the fall of South Vietnam. PAVN buildup under the 1973 ceasefire, the Central Highlands collapse from 10 March 1975, the fall of Hue and Da Nang, Thieu's resignation, Operation Frequent Wind, the fall of Saigon on 30 April 1975, and reunification on 2 July 1976.

Generated by Claude Opus 4.89 min answerUpdated 2026-06-27

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this dot point is asking

NESA expects you to explain the collapse of South Vietnam in 1975 and the reunification of Vietnam. Strong answers cover the failure of the Paris Peace Accords to hold, the PAVN buildup under the ceasefire, the cutting of US aid, the Thieu regime's strategic errors, the fall of the Central Highlands and the north, the fall of Saigon on 30 April 1975, and reunification on 2 July 1976.

In plain English

By 1973 the Americans had signed a peace deal and gone home, but the deal let North Vietnam's army stay parked inside South Vietnam. Picture a referee blowing the final whistle and walking off while one team keeps all its players on the field. Worse, the US Congress kept cutting the money it sent to the South, so the southern army ran short of fuel and ammunition and had to leave its planes and helicopters on the ground - and that army had been trained to fight like the Americans, leaning on air power it no longer had.

In early 1975 the North tested whether the US would come back. It grabbed a whole province and nothing happened, so it launched a full attack. The southern president then made a panicked decision to pull his troops out of the central mountains down one bad road, and the retreat fell apart into a stampede called "the convoy of tears". After that the South collapsed like dominoes - city after city - until North Vietnamese tanks smashed through the gates of the palace in Saigon on 30 April 1975. A year later, on 2 July 1976, the two halves were joined into one communist country and Saigon was renamed Ho Chi Minh City.

The answer

The failure of the Accords

The 27 January 1973 Paris Peace Accords broke down almost immediately. The ceasefire was violated by both sides; the ICCS commission was paralysed (Canada withdrew in July 1973). The Council of National Reconciliation never functioned.

PAVN forces in the south at the ceasefire (around 145,000) grew to around 200,000 by late 1974. The Trail was upgraded into the 8-metre paved Truong Son Highway (Highway 14, completed 1973 to 1975). Soviet and Chinese deliveries of T-54 tanks, BM-21 rocket artillery, MiG-21 fighters, and SA-7 shoulder-fired missiles continued.

In the United States, Watergate paralysed the Nixon administration. Nixon resigned on 9 August 1974. Congress cut military aid to South Vietnam from $2.27 billion (FY1973) to$ 1.01 billion (FY1974) to $700 million (FY1975, against an administration request of$ 1.4 billion). The promise that Nixon had made to Thieu privately, to enforce the Accords by air power, could not be honoured.

ARVN was rationing fuel; helicopters and fighters were grounded. Defensive minefields were thinned. Air mobility, the cornerstone of the war for a decade, evaporated.

Phuoc Long

In December 1974 PAVN attacked Phuoc Long Province, about 110 kilometres north of Saigon. The provincial capital, Phuoc Binh, fell on 6 January 1975. It was the first whole province lost since 1965.

Hanoi watched the US response. President Gerald Ford expressed regret; there were no B-52 strikes. The Politburo, meeting in Hanoi from 8 to 30 October 1974 and reconvening in late December, concluded that the United States would not return. The Politburo authorised a two-year plan: a major offensive in 1975 to set the conditions for a decisive victory in 1976.

The Central Highlands

General Van Tien Dung, PAVN Chief of Staff, took command of Campaign 275. The plan: attack Ban Me Thuot, the population centre of the Central Highlands, to lure ARVN reinforcements south, then defeat them in detail.

PAVN forces (3 divisions, around 75,000 troops) struck on 10 March 1975. Ban Me Thuot fell on 11 March 1975 in 32 hours. President Nguyen Van Thieu, conferring with senior commanders at Cam Ranh Bay on 14 March, ordered the evacuation of Pleiku, Kontum, and the rest of the Central Highlands south of Da Nang.

The retreat down Route 7B, a poor road through PAVN ambushes, became "the convoy of tears". Around 60,000 II Corps troops withdrew with around 400,000 civilians. PAVN harassment, panic, and disintegration of unit cohesion turned the retreat into a rout. ARVN II Corps effectively ceased to exist.

The northern collapse

PAVN exploited the disintegration immediately. I Corps, holding the north, was outflanked. Hue, with no defensible perimeter, fell on 25 March 1975. Civilian refugees flooded into Da Nang.

Da Nang, the second city of South Vietnam, fell on 29 March 1975 amid chaos. American consul Albert Francis directed an emergency air and sea evacuation; the last World Airways 727 flight from Da Nang on 29 March was famously stormed by ARVN deserters. Around 70,000 civilians escaped by sea.

ARVN losses in March 1975: around 150,000 troops killed, captured, or deserted; around half of ARVN's combat strength. PAVN now had 17 divisions in the south.

The Ho Chi Minh Campaign

The Politburo renamed Campaign 275 the "Ho Chi Minh Campaign" on 1 April 1975. The objective was Saigon by 19 May, Ho's birthday. General Van Tien Dung commanded; Le Duc Tho served as the Politburo's political commissar.

The 18th ARVN Division under General Le Minh Dao made a stand at Xuan Loc on Highway 1, 60 kilometres east of Saigon, from 9 to 21 April 1975. The defence held off three PAVN divisions for 12 days at heavy cost; Xuan Loc fell on 20 to 21 April.

Thieu resigned on the evening of 21 April 1975 in a bitter speech blaming the United States. Vice President Tran Van Huong succeeded; on 28 April he handed power to General Duong Van Minh (the same Minh who had led the 1963 coup), in the hope that "Big Minh" might negotiate a soft landing. PAVN was not interested in negotiations.

Operation Frequent Wind and the fall

Operation Frequent Wind, the helicopter evacuation of the last Americans and selected Vietnamese, was triggered on 29 April 1975 when Tan Son Nhut airbase was hit by PAVN rockets. Bing Crosby's "White Christmas" on the American Radio Service was the signal. From the embassy compound at 4 Thong Nhut Boulevard and the Defence Attache Office at Tan Son Nhut, around 7,000 people were lifted to ships of Task Force 76 offshore. Hubert Van Es's photograph of a CIA Air America helicopter on the roof at 22 Gia Long Street became iconic.

Around 5,500 Vietnamese were evacuated by Frequent Wind, far short of the 200,000-plus who had worked for the Americans. The last US Marines left the embassy roof at 0753 on 30 April 1975.

PAVN T-54 tanks (the leading tank was number 843) crashed through the gates of the Presidential Palace on Norodom Boulevard at 1130 on 30 April 1975. General Duong Van Minh surrendered on Saigon Radio. The war was over.

Reunification

South Vietnam was briefly governed as the Provisional Revolutionary Government (1975 to 1976). The reunification elections held on 25 April 1976 produced a single national assembly. The Socialist Republic of Vietnam was proclaimed on 2 July 1976 with Hanoi as the capital and Saigon renamed Ho Chi Minh City.

The new regime imposed re-education camps; around 200,000 to 300,000 former ARVN officers and southern officials were detained, many for years. The "boat people" exodus began (around 800,000 by 1979, perhaps 200,000 dying at sea). Australia accepted around 70,000 Vietnamese refugees from 1975 onwards under the Fraser government.

Historiography

George Veith (Black April, 2012) is the standard military history of the 1975 campaign from the southern side.

Van Tien Dung (Our Great Spring Victory, 1976) is the commander's memoir.

Larry Berman on the politics of the abandonment.

Frank Snepp (Decent Interval, 1977) is the CIA analyst's account of the chaotic evacuation.

Historians divide over contingency. George Veith (Black April, 2012) insists the defeat was not foreordained: ARVN fought well where well led (Xuan Loc), and better US support or steadier southern command might have prolonged the war. George Herring counters that the south was structurally unviable - built on US firepower it could never replace - so withdrawal made collapse only a matter of time. The 14 March evacuation order sits at the centre of this debate: a contingent blunder, or the moment a doomed structure simply gave way.

The chronology, March to April 1975

Model exam responses

A. Source response (5 marks). Source: Hubert Van Es's photograph of Vietnamese evacuees climbing a ladder to a CIA Air America helicopter on a Saigon rooftop, 29 April 1975. Assess the usefulness of this source for a historian studying the fall of South Vietnam.

The photograph is eyewitness press evidence from the final day of the evacuation (29 April 1975), taken by a UPI photographer on the spot, so it is strong direct evidence of the chaos and desperation of Operation Frequent Wind - the improvised rooftop lift, the crowd far larger than the aircraft could take. It is highly useful for the human reality of the collapse and for the gap between the 200,000-plus Vietnamese who had worked for the Americans and the roughly 5,500 actually flown out. Its limitation is scope: a single rooftop image captures the symptom, not the causes - it cannot show the aid cuts, the PAVN buildup under the 1973 Accords, or Thieu's Highlands blunder that had already destroyed ARVN. Read critically, the source is excellent for the texture and failure of the evacuation, but must be combined with own knowledge of the military collapse to explain why the fall happened.

Marker's note: a top response fixes origin and date, separates what the image is useful FOR (the evacuation's chaos) from what it cannot show (the structural causes), anchors this in specific own knowledge with figures, and ends in a judgement rather than describing the photo.

B. Essay paragraph (from a 25-mark response on whether the fall owed more to American withdrawal or to DRV military superiority).

American withdrawal was the condition that made every later defeat possible. The Paris Accords of January 1973 ended US combat involvement yet left around 145,000 PAVN troops inside the south, and over the next two years Congress cut military aid from $2.27 billion to $700 million while Nixon's resignation in August 1974 voided his private pledge to re-intervene by air. The effect on an ARVN built in the American image - dependent on air mobility, artillery and fuel - was crippling: helicopters were grounded and ammunition rationed. When PAVN took Phuoc Long in January 1975 and President Ford did nothing, Hanoi correctly read that the guarantee was dead. As George Herring argues, the south had been made structurally unviable, a state that could not survive the removal of the firepower that sustained it; the PAVN offensive that followed exploited a collapse that withdrawal had already set in motion.

Marker's note: the paragraph argues a single proposition (withdrawal as the enabling condition), supports it with dated figures, and uses a named historian to frame the structural reading rather than as decoration. Sustained argument plus historiography is what lifts a paragraph into Band 6.

Command words and weaving historiography

Read the verb first. "Account for" and "Assess the reasons" want CAUSES weighed and ranked (aid cuts vs PAVN buildup vs Thieu's errors), not a chronicle; "To what extent / Evaluate" want a JUDGEMENT defending a thesis; "Assess the usefulness/reliability" of a source wants ORIGIN, MOTIVE and PERSPECTIVE, then a verdict - run O-M-P-U (Origin, Motive, Perspective, Usefulness/limitation). For the iconic 1975 images (the rooftop helicopter, the convoy of tears) always ask what they capture and what they conceal. Weave historians as a clash, not a list: set structural disengagement (Herring - the south could never stand alone) against contingency and southern agency (Veith - ARVN fought hard where well led, and defeat was not foreordained), then say which carries more weight and why. One historian used in genuine tension beats five name-dropped.

In one sentence

South Vietnam collapsed in 1975 because the Paris Peace Accords left PAVN in the south, Congress cut US military aid by around two thirds across 1974 to 1975, Thieu's botched evacuation of the Central Highlands on 14 March 1975 turned a setback into a rout, the Ho Chi Minh Campaign drove on Saigon through April, Operation Frequent Wind lifted the last Americans and 5,500 Vietnamese from rooftops on 29 to 30 April, PAVN T-54 number 843 crashed through the Presidential Palace gates at 1130 on 30 April 1975, and Vietnam was reunified as the Socialist Republic of Vietnam on 2 July 1976.

Examples in context

Example 1. The Ho Chi Minh Campaign (March to April 1975). PAVN General Van Tien Dung's 1975 spring offensive collapsed ARVN resistance from Ban Me Thuot (10 March) to Saigon (30 April). George Herring (America's Longest War, 5th ed. 2014) and Pierre Asselin (Vietnam's American War, 2018) detail Hanoi's calculated assessment that Nixon's resignation in August 1974 and congressional cuts to aid had ended the credibility of American re-intervention.

Example 2. Operation Frequent Wind (29 to 30 April 1975). The helicopter evacuation lifted around 7,000 American and Vietnamese personnel from the US Embassy and DAO compound. Hugh Van Es's UPI photograph of the rooftop ladder at 22 Gia Long Street became iconic. Frank Snepp (Decent Interval, 1977), CIA station analyst, drew on internal cables to indict the evacuation planning. The fall produced an exodus of approximately 130,000 South Vietnamese to the United States in 1975 alone.

Try this

Q1. Source A is Hugh Van Es's photograph of the helicopter evacuation from 22 Gia Long Street (29 April 1975). Using Source A and your own knowledge, explain the collapse of South Vietnam in 1975. [5 marks]

What the marker wants. Identify Operation Frequent Wind; cite the Ho Chi Minh Campaign; link to congressional aid cuts.

Q2. Evaluate the extent to which the fall of Saigon was the result of American withdrawal rather than DRV military superiority. [25 marks]

What the marker wants. Weigh ARVN dependency, congressional aid reductions, and PAVN conventional capacity; use Herring, Asselin.

Q3. Compare the views of George Herring and Frank Snepp on the role of the United States in the 1975 collapse. [10 marks]

What the marker wants. Herring (structural disengagement) versus Snepp (specific intelligence and evacuation failures); judgement.

Exam-style practice questions

Practice questions written in the style of NESA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

Practice (NESA)15 marksAccount for the collapse of South Vietnam in 1975.

Show worked answer →

Needs a clear thesis, dated evidence, and integration of military and political factors.

Thesis: South Vietnam collapsed in 1975 because the Paris Peace Accords left PAVN forces in the south, US aid was cut to a fraction of what was promised, the Thieu regime made strategic blunders in March 1975, and the PAVN final offensive was better resourced and better commanded than ARVN could resist.
The setup: PAVN built up around 200,000 troops in the south under the 1973 ceasefire. Congress cut US aid to Saigon to $700 million for FY1975. ARVN faced fuel rationing and grounded aircraft. Nixon resigned 9 August 1974; the secret pledge to enforce the Accords was impossible to keep.
Phuoc Long: PAVN took Phuoc Long Province in January 1975, the first whole province lost since 1965. The Ford administration's failure to respond signalled the US guarantee was dead.
Central Highlands: Campaign 275 took Ban Me Thuot on 11 March 1975. Thieu ordered an evacuation on 14 March. "The convoy of tears" down Route 7B saw around 60,000 troops and 400,000 civilians flee with catastrophic losses.
Northern collapse: Hue fell on 25 March, Da Nang on 29 March 1975. Around half of ARVN ceased to exist by the end of March.
Final offensive: Xuan Loc fell on 20 April after the 18th Division's stand. Thieu resigned 21 April. Operation Frequent Wind evacuated around 7,000 people from 29 April. PAVN tank 843 crashed through the Presidential Palace gates at 1130 on 30 April 1975.
Reunification: The Socialist Republic of Vietnam was proclaimed on 2 July 1976.

Markers reward the 30 April 1975 date, the convoy of tears, and Frequent Wind.

Practice questions

Original practice questions graded from foundation to exam level, each with a full worked solution. Try them before revealing the solution.

foundation3 marksOutline three ways the 1973 Paris Peace Accords left South Vietnam vulnerable to collapse.

Show worked solution →

A 3-mark "outline" wants three distinct, correctly dated points, each in a sentence.

PAVN forces stayed in the south: The Accords (27 January 1973) contained no withdrawal of the roughly 145,000 PAVN troops already in the south, which grew to around 200,000 by late 1974.
No enforcement machinery worked: The ICCS commission was paralysed (Canada withdrew in July 1973) and the Council of National Reconciliation never functioned, so ceasefire violations went unchecked.
The US guarantee was hollow: Nixon's private pledge to enforce the Accords by air power could not be honoured once Watergate and his resignation (9 August 1974) and congressional aid cuts removed the means and the will.
Marking criteria: 1 mark each for three distinct, correctly explained points; do not simply narrate the 1975 offensive.

foundation4 marksExplain how the cutting of US military aid contributed to the collapse of South Vietnam.

Show worked solution →

A 4-mark "explain" needs a cause-and-effect chain with specific figures.

The cuts: Congress reduced US military aid to Saigon from $2.27 billion (FY1973) to $1.01 billion (FY1974) to $700 million (FY1975), against an administration request of $1.4 billion - a fall of around two thirds in two years.
The military effect: ARVN had been built as a US-style force dependent on air mobility, artillery and fuel. The cuts forced fuel rationing, grounded helicopters and fighters, and thinned defensive minefields, stripping ARVN of the firepower and mobility that had held the line.
The political effect: The reductions, with Nixon's resignation, signalled to Hanoi that American re-intervention was over - confirmed when Ford did not respond to the loss of Phuoc Long in January 1975.
Marking criteria: 1 mark for the scale of the cuts with figures; 1 mark for the logistical effect on ARVN; 1 mark for the signal sent to Hanoi; 1 mark for linking aid to the collapse.

core5 marksSource A (paraphrased, owned): A southern military history of the 1975 campaign argues that the rout of the Central Highlands was not inevitable but was triggered by President Thieu's sudden order on 14 March to abandon Pleiku and Kontum and pull II Corps south down a single poor road, which collapsed into panic before PAVN had to fight for it. Using Source A and your own knowledge, explain why the Central Highlands fell so quickly in March 1975. [5 marks]

Show worked solution →

A 5-mark "explain ... using the source" wants the source decoded, then linked to own knowledge.

Decode the source: Source A blames Thieu's own decision: the 14 March order to evacuate the Central Highlands (made at Cam Ranh Bay) turned a defensible position into a retreat that disintegrated before serious contact.
What happened (own knowledge): General Van Tien Dung's Campaign 275 took Ban Me Thuot on 11 March 1975 in about 32 hours. Thieu's evacuation down Route 7B, a poor road through PAVN ambushes, became "the convoy of tears": around 60,000 II Corps troops and around 400,000 civilians fled, and panic, harassment and lost unit cohesion turned the withdrawal into a rout. II Corps effectively ceased to exist.
The judgement: PAVN planning lured ARVN into a trap, but the speed of the collapse owed as much to Thieu's botched order as to PAVN strength - just as Source A argues.
Marking criteria: 1 mark for reading the source's argument (Thieu's order, not inevitability); 1-2 marks for own knowledge (Ban Me Thuot, Route 7B, convoy of tears); 1 mark for the disintegration of II Corps; 1 mark for a judgement that weighs PAVN planning against ARVN error.

core5 marksSource B (paraphrased, owned): A CIA analyst present in Saigon later argued that the evacuation of 1975 was a planning failure - that Washington, refusing to admit the south was lost, delayed Operation Frequent Wind until the last days and abandoned far more Vietnamese employees than it rescued. Using Source B and your own knowledge, assess the usefulness of this view for understanding the fall of Saigon. [5 marks]

Show worked solution →

A 5-mark "assess the usefulness" question rewards origin and perspective plus own knowledge, ending in a judgement.

Origin and perspective: Source B is the insider, critical perspective of a CIA station analyst (the position of Frank Snepp, Decent Interval, 1977) who saw the cables - useful because it draws on direct access and exposes the gap between official optimism and reality on the ground.
Corroboration from own knowledge: It fits the record: Frequent Wind was only triggered on 29 April 1975 after Tan Son Nhut was rocketed; around 7,000 were lifted in a single night, but only around 5,500 were Vietnamese, far short of the 200,000-plus who had worked for the Americans, and the last Marines left the roof at 0753 on 30 April.
Limitation: As a participant indicting his own employer, Snepp has a perspective that may overstate avoidable failure and understate the structural cause - the south was collapsing faster than any orderly evacuation could match once the Highlands fell.
Judgement: Highly useful as eyewitness evidence of the chaotic, belated evacuation, but it must be read alongside the broader collapse: the rooftop scenes were the symptom of a regime already militarily destroyed.
Marking criteria: 1 mark for origin/perspective (CIA insider, critical); 1-2 marks for own knowledge corroborating the delay and the numbers; 1 mark for a limitation; 1 mark for a judgement on usefulness.

core6 marksAssess the significance of the Ho Chi Minh Campaign in the collapse of South Vietnam in 1975.

Show worked solution →

A 6-mark "assess the significance" wants a judgement supported by dated stages, not a narrative.

The campaign: The Politburo renamed Campaign 275 the "Ho Chi Minh Campaign" on 1 April 1975 under General Van Tien Dung, aiming to take Saigon by Ho's birthday (19 May).
Its stages: It exploited the Highlands rout: Hue fell on 25 March and Da Nang on 29 March, destroying around half of ARVN. The 18th Division's 12-day stand at Xuan Loc (9 to 21 April) was the last serious resistance; Thieu resigned on 21 April; PAVN T-54 number 843 crashed the Presidential Palace gates at 1130 on 30 April 1975.
Significance: The campaign converted a regional setback into the final conquest in under two months, achieving by conventional armour and artillery what guerrilla war had not - and proving the south could not survive without US firepower.
Limitation on its significance: The campaign succeeded only because the prior conditions - the aid cuts, the PAVN buildup under the Accords, and Thieu's Highlands blunder - had already broken ARVN; the offensive delivered the collapse rather than causing it.
Marking criteria: 1 mark for dating and naming the campaign; 2 marks for its stages with dates; 1-2 marks for a judgement of significance; 1 mark for weighing it against the enabling conditions.

exam25 marksEvaluate the extent to which the fall of South Vietnam in 1975 was caused by American withdrawal rather than by the military superiority of North Vietnam.

Show worked solution →

This is an extended-response/essay. Markers reward a sustained, evidence-based argument that addresses the comparison directly and weaves in historiography - not a narrative.

Band-6 PLAN

Thesis. The fall of the south was overdetermined: American withdrawal and PAVN superiority were not rival causes but two halves of one process - the US disengagement removed the firepower that had masked ARVN's structural weakness, and PAVN's conventional buildup then exploited the opening. Withdrawal was the necessary condition; PAVN superiority was the sufficient one. The decisive factor was the south's dependence, which made withdrawal fatal.
Argument 1 - American withdrawal as the enabling cause. The Paris Accords (1973) left PAVN in the south and provided no enforcement; congressional aid cuts ($2.27bn to $700m, FY1973 to FY1975) and Nixon's resignation (August 1974) stripped both the means and the credibility of US re-intervention. Evidence: Ford's silence over Phuoc Long (January 1975) told Hanoi the guarantee was dead.
Argument 2 - PAVN superiority as the sufficient cause. By 1975 PAVN fielded around 200,000 troops in the south, the paved Truong Son Highway, and Soviet and Chinese armour and artillery (T-54s, BM-21s). Campaign 275 took Ban Me Thuot in 32 hours; the Ho Chi Minh Campaign drove on Saigon with 17 divisions. This was conventional, not guerrilla, victory.
Argument 3 - The decisive variable: ARVN dependence and Thieu's errors. ARVN had been built as a US-style force reliant on air mobility and firepower; once that was withdrawn it could not function. Thieu's botched 14 March evacuation of the Highlands turned a setback into the rout of II Corps - showing that ARVN's collapse was as much self-inflicted as imposed.
Historiography. George Herring (America's Longest War) stresses structural disengagement - the south could never stand alone. Frank Snepp (Decent Interval, 1977) indicts specific US intelligence and evacuation failures. George Veith (Black April, 2012) restores agency to the southern army and its commanders, arguing ARVN fought hard where led well (Xuan Loc) and that defeat was contingent, not foreordained.
Judgement. Weigh structural disengagement (Herring) against contingent failure (Veith): US withdrawal made collapse possible and PAVN superiority made it certain, but the proximate trigger was the south's fatal dependence, exposed the moment American firepower was removed.

MODEL PARAGRAPH (Argument 3)

The clearest sign that the collapse was a failure of dependence rather than a simple PAVN conquest lies in the rout of the Central Highlands in March 1975. After General Van Tien Dung's forces took Ban Me Thuot in roughly 32 hours on 11 March, President Thieu, conferring at Cam Ranh Bay on 14 March, ordered II Corps to abandon Pleiku and Kontum and withdraw south down Route 7B - a single poor road through PAVN ambushes. The retreat became "the convoy of tears": around 60,000 troops and 400,000 civilians fled, panic and lost cohesion turning a withdrawal into a disintegration before PAVN had to fight for the ground. That an army could dissolve so fast reveals how completely ARVN had been hollowed by the aid cuts and how brittle command had become without US support. As George Veith argues, the southern army could fight hard where it was well led, as the 18th Division proved at Xuan Loc; but stripped of American firepower and saddled with strategic blunders, its defeat owed as much to dependence and error as to any irresistible northern superiority.

Marker's note. A band-6 response sustains the comparison throughout (always weighing "American withdrawal" against "DRV superiority" rather than narrating the fall), anchors every claim in specific dated evidence, sets at least two historians in genuine tension (Herring's structural disengagement vs Veith's contingency and southern agency), and reaches a graded judgement. Narrating the 1975 campaign without arguing why the south could not stand alone caps the response in the middle bands.