South Vietnam stands alone, 1974–1975

Total U.S. withdrawal

As Stanley Karnow noted, Americans "turned against the war long before America's political leaders did." Doubts began surfacing in Congress. In December 1974, it passed the Foreign Assistance Act of 1974, which cut off all military funding to the South Vietnamese government. The act fixed the numbers of U.S. military personnel allowed in Vietnam: 4000 within six months of enactment and 3000 within one year. Robert McNamara writes that " there is no evidence that the South Vietnamese would ever have been able to accomplish on their own what they failed to achieve with massive American assistance. The level of congressional funding was irrelevant … The Nixon administration, like the Johnson administration before it, could not give the South Vietanmese the essential ingredient for success: genuine indigenous political legitimacy."[104] Richard Nixon resigned due to the Watergate Scandal. President Gerald Ford signed the act into law.

By 1975, South Vietnamese Army was much larger on paper than its opponent. But they faced a well-organized, highly determined and well-funded North Vietnam. Much of the North's material and financial support came from the communist block. Within South Vietnam, there was increasing chaos. The withdrawal of the American military had compromised an economy dependant on U.S. financial support and the presence of large numbers of U.S. troops. Along with the rest of the non-oil exporting world, South Vietnam suffered from the price shocks caused by the Arab oil embargo and the subsequent global recession.

Between the signing of the 1973 Paris Peace Accord and late 1974 both antagonists had been satisfied with minor land-grabs. The North Vietnamese, however, were growing impatient with the Thieu regime, which remained intransigent on the issue of national elections. Hanoi was also concerned that the U.S. would, once again, support its former ally if large scale operations were resumed.

By late 1974, the Politburo gave its permission for a limited VPA offensive from Cambodia into Phuoc Long Province. The strike was designed to solve local logistical problems, gauge the reaction of Saigon forces and determine if the U.S. would return to the fray. In late December and early January the offensive kicked off and Phuoc Long Province quickly fell to the VPA. There was considerable relief when American air power did not return. The speed of this success forced the Politburo to reassess the situation. It was decided that operations in the Central Highlands would be turned over to General Van Tien Dung and that Pleiku should be seized, if possible. Before he left for the south, General Van was addressed by First Party Secretary Le Duan: "Never have we had military and political conditions so perfect or a strategic advantage as great as we have now."

Campaign 275

On 10 March, 1975, the General Dung launched Campaign 275, a limited offensive into the Central Highlands, supported by tanks and heavy artillery. The target was Ban Me Thuot, in Daklak Province. If the town could be taken, the provincial capital of Pleiku and the road to the coast would be exposed for a planned campaign in 1976. The ARVN proved incapable of resisting the onslaught and its forces collapsed on 11 March. Once again, Hanoi was surprised by the speed of their success. Van now urged the Politburo to allow him to seize Pleiku immediately and then turn his attention to Kontum. He argued that with two months of good weather remaining until the onset of the monsoon, it would be irresponsible to not take advantage of the situation.

President Nguyen Van Thieu, a former general, now made a strategic blunder. Fearful that his forces would be cut off in the north by the attacking communists, Thieu ordered a retreat. The president declared this to be a "lighten the top and keep the bottom" strategy. But in what appeared to be a repeat of Operation Lam Son 719, the withdrawal soon turned into a bloody rout. While the bulk of ARVN forces attempted to flee, isolated units fought desperately. ARVN General Phu abandoned Pleiku and Kontum and retreated toward the coast, in what became known as the "column of tears". As the ARVN tried to disengage from the enemy, refugees mixed in with the line of retreat. Roads and bridges, already damaged by years of conflict, slowed Phu's column. As the North Vietnamese forces approached, panic set in. Often abandoned by their officers, the soldiers and civilians were shelled incessantly. The retreat degenerated into a desperate scramble for the coast. By 1 April the "column of tears" was all but annihilated. It marked one of the poorest examples of a strategic withdrawal in modern military history.

On 20 March, Thieu reversed himself and ordered Hue, Vietnam's third-largest city, be held at all costs. Thieu's contradictory orders confused and demoralized his officer corp. As the North Vietnamese launched their attack, panic set in and ARVN resistance withered. On 22 March, the VPA opened the siege of Hue. Civilians flooded the airport and the docks hoping for any mode of escape. Some even swam out to sea to reach boats and barges anchored offshore. In the confusion, routed ARVN soldiers fired on civilians to make way for their retreat. On 31 March, after a three-day battle, Hue fell. As resistance in Hue collapsed, North Vietnamese rockets rained down on Da Nang and its airport. By the 28 March, 35,000 VPA troops were poised to attack the suburbs. By the 30th, 100,000 leaderless ARVN troops surrendered as the VPA marched victoriously through Da Nang. With the fall of the city, the defense of the Central Highlands and Northern provinces came to an end.

Final North Vietnamese offensive

With the northern half of the country under their control, the Politburo ordered General Van to launch the final offensive against Saigon. The operational plan for the Ho Chi Minh Campaign called for the capture of Saigon before 1 May. Hanoi wished to avoid the coming monsoon and prevent any redeployment of ARVN forces defending the capital. Northern forces, their morale boosted by their recent victories, rolled on, taking Nha Trang, Cam Ranh, and Da Lat.

On 7 April, three North Vietnamese divisions attacked Xuan-loc, 40 miles (64 km) east of Saigon. The next day a rogue South Vietnamese pilot bombed the presidential palace in Saigon. No one was injured. The North Vietnamese met fierce resistance at Xuan-loc from the ARVN 18th Division. For two bloody weeks, severe fighting raged as the ARVN defenders, in a last-ditch effort, tried to block their advance. By 21 April, however, the exhausted garrison surrendered. An embittered and tearful President Thiệu resigned on the same day, declaring that the United States had betrayed South Vietnam. He left for Taiwan on 25 April, leaving control of the government in the hands of General Duong Van Minh. At the same time, North Vietnamese tanks had reached Bien Hoa and turned towards Saigon, brushing aside isolated ARVN units along the way.

By the end of April, the Army of the Republic of South Vietnam had collapsed on all fronts. Thousand of refugees streamed southward, ahead of the main communist onslaught. On the 27th, 100,000 North Vietnamese troops encircled Saigon. The city was defended by about 30,000 ARVN troops. To hasten a collapse and foment panic, the VPA shelled the airport and forced its closure. With the air exit closed, large numbers of civilians found that they had no way out.

Fall of Saigon

Chaos, unrest, and panic ensued as hysterical South Vietnamese officials and civilians scrambled to leave Saigon. Martial law was declared. American helicopters began evacuating South Vietnamese, U.S. and foreign nationals from various parts of the city and from the U.S. embassy compound. Operation Frequent Wind had been delayed until the last possible moment, because of U.S. Ambassador Graham Martin's belief that Saigon could be held and that a political settlement could be reached. Operation Frequent Wind was arguably the largest helicopter evacuation in history. It began on April 29, in an atmosphere of desperation, as hysterical crowds of Vietnamese vied for limited seats. Martin pleaded with the Washington to dispatch $700 million in emergency aid to bolster the regime and help it mobilize fresh military reserves. But American public opinion had long soured on this conflict halfway around the world.

In the U.S., South Vietnam was now perceived as doomed. President Gerald Ford gave a televised speech on April 23, declaring an end to the Vietnam War and all U.S. aid. Operation Frequent Wind continued around the clock, as North Vietnamese tanks breached defenses on the outskirts of Saigon. The song "White Christmas" was broadcast, as the final signal for withdrawal. In the early morning hours of 30 April, the last U.S. Marines evacuated the embassy by helicopter, as civilians swamped the perimeter and poured into the grounds. Many of them had been employed by the Americans and were now left to their fate.

On April 30, 1975, VPA troops overcame all resistance, quickly capturing key buildings and installations. A tank crashed through the gates of the Presidential Palace and at 11:30 a.m. local time the NLF flag was raised above it. Thieu's successor, President Dương Văn Minh attempted to surrender, but VPA Colonel Bui Quang Than informed him that he had nothing left to surrender. Minh then issued his last command, ordering all South Vietnamese troops to lay down their arms.