Fall of South Vietnam

The Paris Peace Accords of January 27, 1973, were the beginning of the end of South Vietnam. There would be an immediate in-place permanent cease-fire. The U.S. agreed to withdraw all its troops in 60 days (but could continue to send military supplies); North Vietnam was allowed to keep its 200,000 troops in the South but was not allowed to send new ones.

Saigon had still not been able to create widespread popular support or run an effective administration. Its weaknesses were compounded by exaggerated confidence that the U.S. would return if and when needed.Although it was well-armed — its 2100 modern aircraft comprised the fourth largest air force in the world — the ARVN had never learned to fight large-scale operations against a conventional enemy.

Invasion and the fall of the south, 1975

North invades South, 1975, using bases in Cambodia and Laos, and across DMZ

Starting in March, 1975, Hanoi sent 18 divisions, with 300,000 of its 700,000, soldiers to invade the South again, in conventional fashion with marching armies spearheaded by 600 Russian-built tanks and 400 pieces of artillery, and using a conventional logistics structure. It had mobile air defenses including anti-aircraft artillery and possibly surface-to-air missiles. It had clear objectives, with political officers ready to deal with those that did not follow the plan.

The South Vietnamese military, however, had unclear goals, even on operational issues of when to trade territory for time. It had not learned to exercise command and control at the level of a national effort. The South's doctrine was called "light at the top, heavy at the bottom", meaning that it would resist lightly in the northern party of the country (I Corps), but stiffen resistance as the North extended. That was an attritional strategy, and the DRV had not broken under the much heavier attrition imposed by U.S. troops.

Its air force, however, performed poorly, and often abandoned its bases.

The ARVN, with 1.1 million soldiers, still had a 2-1 advantage in combat soldiers and 3-1 in artillery, but it misused its resources badly. Some ARVN units fought well; most collapsed under the 16-division onslaught. The North Vietnamese regular army, the PAVN, began a full-scale offensive by seizing Phuoc Long Province in January, 1975. In March, 1975, they continued their offensive campaigns by conducting diversionary attacks in the north threatening Pleiku and then attacking the lightly defended South Vietnamese rear area.

The PAVN captured the Central Highlands and moved to the sea to divide the country. The PAVN blocked the South Vietnamese attempt to retreat from the Central Highlands and destroyed the ARVN II corps. Of the 314 M-41 and M-48 ARVN tanks assigned to the Highlands, only three made it through to the coast.

President Thieu released written assurances, dated April 1973, from President Nixon that the U.S. would "react vigorously" if North Vietnam violated the truce agreement. But Nixon had resigned in August 1974 and his personal assurances were meaningless; After Nixon made the promises, Congress had prohibited the use of American forces in any combat role in Laos, Cambodia, and Vietnam without prior congressional approval. This was well known to the Saigon government. The Ford Administration, with specific legislative restrictions against direct aid and a lack of public support, was limited to some fnancial aid.

About 140,000 refugees managed to flee the country, chiefly by boat. The PAVN then concentrated its combat power to attack the six ARVN divisions isolated in the north. After destroying these divisions, the PAVN launched its "Ho Chi Minh Campaign" that with little fighting seized Saigon on April 30, ending the war.

No American military units had been involved until the final days, when Operation FREQUENT WIND was launched to protect the evacuation of Americans and 5600 senior Vietnamese government and military officials, and employees of the U.S. The 9th Marine Amphibious Brigade would enter Saigon to evacuate the last Americans from the American Embassy to ships of the Seventh Fleet.

Vietnam was unified under Communist rule, as nearly a million refugees escaped by boat. Saigon was renamed Ho Chi Minh City.