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.

Correlation of Forces

While the PAVN and ARVN had approximately the same number of troops, the ARVN, needing to support a fixed defensive system as well as its mobile combat forces, could field 13 operational divisions compared to 13 in the ARVN.

While U.S. troops were gone, U.S. funding for South Vietnam, and resupply, had drastically decreased. The PAVN, however, had been getting abundant resources from the Soviet Union and China. Due to a lack of spare parts, 30 to 40 percent of ARVN equipment was inoperative on any given day, while ammunition shortages cut fire support capabilies by 60 percent.

The Decision to Invade

In December 1974, the North Vietnamese Politburo gave command of the main assault to GEN Van Tien Dung, whose patron was Vo Nguyen Giap. Dung had been the chief of staff and head of logistics at Dien Bien Phu, and was considered a solid but not brilliant leader.

Preliminaries

In January, the PAVN 301st Corps began a multidivision operation in the Phuoc Long province. First, a diversionary attack was made at Tay Ninh; LTG Du Quoc Dong, used his reserve to defend enemy's attack on Tay Ninh. Initial requests for strategic reserve (airborne and marine) troops were at first refused by President Thieu, but, on January 5, 250 Rangers from the 81st airborne Rangers made an air assault to reinforce Phuoc Long city. Without air, artillery, or armored support, they failed to reach their destination, and Phuoc Long City surrendered on the 6th

The main attack, on December 13, involved the 3rd and 7th Infantry Divisions, with a tank battalion, an artillery regiment, an antiaircraft regiment, and sapper units under corps control. The NVA 7th Infantry Division moved towards Bo Duc, Don Luan, and Phuoc Long City, with the 3rd Infantry Division simultaneously moving to capture Duc Phong, and Phuoc Long City. Phuoc Binh airfield and the main firebase were suppressed by artillery, and the isolated garrisons destroyed individually.

The attack isolated the province by cutting National Highway 14. The PAVN were not impressed by the alerting of U.S. Marines on Okinawa, and the moving of an aircraft carrier into range. Thieu told the cabinet that while it could be taken back, it would not be worthwhile, although GEN Cao Van Vien, chief of the Joint General Staff, warned that it would encourage the North Vietnamese. The RVN Air Force had performed poorly there, losing 20 aircraft to groundfire yet not pressing in to hit targets accurately.

After this result, Le Duan personally told the Politburo that the next step should be to move against Darlac Province and its capital, Ban Me Thuot, and then toward the sea. From the Politburo meeting, Le Duc Tho took the idea to the senior military committee, where Vo Nguyen Giap joined the discussion, agreeing generally but wanting a deceptive move, as well, against Tai Nguyen. Dung left for his field headquarters on February 5.

North Vietnamese preparation

Dung's force had 18 divisions, with 300,000 of its 700,000, soldiers, conventionally organized with infantry, tanks and artillery.

The basic operational plan mirrored that which preceded the Battle of the Ia Drang: drive through Central Vietnam to the sea, cutting South vietnam in half. One important difference from 1966-7 was that the PAVN had mobile air defenses including anti-aircraft artillery and possibly surface-to-air missiles.

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

South Vietnamese defensive dispositions

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 initial southern strategy, issued by Nguyen Van Thieu, called "light at the top, heavy at the bottom", meaning that it would resist lightly, or abandon, 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.

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

First operational phase

Facing forces under Pham Van Phu, the PAVN feinted at Pleiku, as during the Ia Drang campaign, but sent their main, three-division attack at Ban Me Thuot, overwhelming it in a one-day battle on March 10.

There was strategic surprise on both sides. The South Vietnamese had not been expecting a major invasion, and assumed, much as in 1972, that the U.S. would assist if one did take place. The North Vietnamese were surpised by the lack of resistance, especially the chaos following the fall of Ban Me Thuot.

Bui Diem, South Vietnam's Ambassador to the United States between 1969 and 1972, said that President Thieu, even after the resignation of Richard M. Nixon, believed that President Gerald Ford did have the authority to order a response. The Ambassador said that Thieu did not really understand American politics and the realities of lack of popular support for intervention. Thieu was getting poor advice; his Assistant for National Security Affairs, Gen. Dan Van Quang, did not want to give Thieu bad news.

The Minster of Planning, Nguyen Tien Hung, was overoptimistic: in presenting his review of proposed 1974-1975 aid to Thieu, Hung saud his sources, "close to the Pentagon", said that $850 million had been earmarked for possible bombing of the North. Bui Diem, and the current Ambassador, Tran Kim Phuong, said this was wishful thinking, but he believed Thieu wanted encouragement and was more prone to listen to Hung than to people with more direct experience with the United StatesThe optimism was increased by military staff reports that procedures had been established for requesting air support from the U.S., although there was no indication that U.S. policy officials approved it. The RAND authors also quoted sources close to Thieu as his not understanding that the U.S. Congress had real power.

Thieu ordered Phu to abandon Pleiku and Kontum and form a new defense line; Phu abandoned his command post, leaving approximately 200,000 refugees to move from the Central Highland to the coast. Phu committed suicide in Saigon when it fell on April 30.

Thieu then changed from the "light at the top" plan, demanding Hue be held to the last. National Highway 1, the only road out of Hue, however, had been blocked by the PAVN. Abandoning land too quickly emboldened the PAVN,

Meanwhile, the PAVN hit attacked at multiple points along the seacoast, at Chu Lai, Quang Ngai, and threatening the major base at Da Nang.

Second Phase

The Politburo directed Dung to "liberate" the south before the monsoon season in May.

CIA officer Frank Snepp believed Nguyen Van Thieu was keeping reserve forces close to Saigon for protection against coups, rather than as military reserves. While CIA intelligence sources in central Vietnam were, at this point, nonexistent. Snepp briefed Ambassador Graham Martin and CIA Station Chief Thomas Polgar that this was the Communists' final, all-out effort, but they considered him pessimistic.

At this point, for many reasons, the immense southward flow of refugees was South Vietnam's chief problem. It was, of course, a humanitarian tragedy; there were no facilities to feed or treat refugees. From a cold military standpoint, however, it also blocked the roads, so, even when an ARVN unit retreated in good order, it had great difficulty linking up with other ARVN forces, so the ARVN had real problems in creating new defensive lines.

The southern PAVN advance split into two columns moving south from Dong Ha, one moving on either side of the Truong Son mountains, and the other continuing south on National Highway 1.

PAVN GEN Dung obtained information that the ARVN would form their main defensive line at Phan Rang, south of Cam Ranh Bay, in the III Corps tactical zone.

South Vietnamese appeals for U.S. support

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.

Evacuation

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.

The end

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