The Paris Peace Accords of the 27th of January 1973 ended the American combat commitment in Vietnam. They did not end the war. The settlement that the Nixon-Kissinger negotiations produced after four years of intermittent negotiations was a substantively asymmetric document — one that allowed the American withdrawal under cover of a face-saving formula, that preserved a notional South Vietnamese state, that left PAVN forces in place in the territory they had captured in the 1972 offensive, and that bound the South Vietnamese state to a settlement that — without continuing American material support — it could not, on the substantive evidence, durably defend. The two further years between Paris and the fall of Saigon in April 1975 were the period during which the substantive American material commitment to the southern state was substantially reduced, the PAVN strategic-logistical position substantively improved, and the southern military and political position substantively deteriorated. The 1975 final offensive, when it came, found the South Vietnamese state structurally unable to resist it.
Linebacker II
The immediate prelude to the Paris settlement was the eleven-day Linebacker II bombing campaign of December 1972 — the so-called Christmas bombing — in which the American Strategic Air Command conducted sustained B-52 strikes against North Vietnamese targets including, for the first time, the Hanoi-Haiphong urban-industrial complex. The campaign ran from the 18th to the 29th of December 1972 (with a Christmas pause); approximately 20,000 tons of bombs were dropped; approximately 1,600 Vietnamese civilians were killed (the figure is contested, with substantially higher estimates from some sources); fifteen B-52s were lost to North Vietnamese surface-to-air missile fire. The substantive political objective was to compel the North Vietnamese negotiators to accept terms that had been substantially agreed in October 1972 but that had been complicated by South Vietnamese objections through November-December. The bombing also was, less avowedly, intended to reassure President Thieu in Saigon that American resolve would be sustained in the post-settlement period — an assurance Nixon and Kissinger believed they could honour but that the subsequent political-domestic events would substantially prevent them from honouring.
The North Vietnamese response to Linebacker II was, on the most substantial subsequent scholarly assessment, less coerced than the American claim suggested. The North Vietnamese had been substantively prepared to settle on the October terms since the autumn; the December bombing complicated their public position without materially altering their negotiating substance. The Paris signing on the 27th of January 1973 included the four principal parties — the United States, the Republic of Vietnam, the Democratic Republic of Vietnam, and the Provisional Revolutionary Government of South Vietnam (the political organ of the NLF) — although the South Vietnamese signature was substantially under American pressure and was accompanied by substantial South Vietnamese reservations.
The settlement
The Paris Accords' substantive provisions: the withdrawal of all American military forces from South Vietnam within sixty days; the return of all American prisoners of war within sixty days; a ceasefire in place (meaning that PAVN forces in the territory they then occupied — approximately a quarter of South Vietnamese territory — remained where they were); the recognition of the political reality of two separate political administrations in southern Vietnam (the Saigon government and the PRG) pending political negotiations between them under an international supervision regime; the prohibition of further American military involvement; the provision for international truce supervision through the International Commission of Control and Supervision (Canada, Hungary, Indonesia, Poland). The military balance the settlement codified — approximately 145,000 PAVN troops in southern territory, approximately 1.1 million in ARVN — was substantially less stable than the formal provisions suggested. PAVN forces could be reinforced through the Ho Chi Minh Trail at a rate that the substantially reduced American aerial-interdiction capacity could not prevent; ARVN could be sustained only by continuing American economic and military assistance whose level was now politically determined in Washington rather than militarily in Saigon.
The aid collapse
The substantial political dynamics in Washington across 1973-74 progressively reduced the American material commitment to South Vietnam. The Watergate scandal — the June 1972 burglary of the Democratic National Committee headquarters at the Watergate office complex in Washington, the subsequent cover-up, the gradual unravelling of the cover-up across 1973-74, and Nixon's resignation on the 9th of August 1974 — substantially weakened the executive's political capacity to defend continued aid commitments to South Vietnam. The Case-Church Amendment of June 1973 prohibited any further American combat involvement in or over Indochina. The Foreign Assistance Acts of 1973 and 1974 substantially reduced the military assistance budget: South Vietnam received approximately $2.27 billion in 1973, $1.01 billion in 1974, and was approved for $300 million in 1975 (subsequently reduced to $700 million authorised but only $400 million actually delivered before the regime's collapse). The reductions, against substantial inflation across 1973-75, produced approximately a 60 per cent reduction in real ARVN purchasing power for ammunition, fuel, and replacement equipment across the eighteen months preceding the 1975 offensive.
The Saigon government's deterioration
The substantive political-military deterioration of the Thieu regime across 1974 was substantial. The reduction in American materiel produced substantive shortages: ARVN units could no longer maintain the operational tempo of 1971-72; fuel shortages reduced air and helicopter operations by approximately 50 per cent; ammunition shortages reduced ARVN artillery fire missions by approximately 75 per cent; spare-parts shortages produced increasing deadlining of aircraft and armoured vehicles. The political climate in Saigon deteriorated correspondingly: the Thieu administration's authoritarian instincts produced renewed repression of the press and the political opposition; the substantial Buddhist-Catholic opposition coalition rebuilt itself across 1974; the corruption visible in the Thieu family's commercial activities became substantially more conspicuous. The Hanoi politburo, assessing this combination across the autumn of 1974, concluded that the political-military conditions for a final offensive were substantially more favourable than they had been in 1972 and that the limited and politically constrained American response capacity in the post-Watergate domestic environment would not produce the air-power intervention of 1972. The decision to launch the final offensive was taken in October-December 1974. The operations of January-April 1975 are the final chapter.
End of Chapter VII