Today, April 30, marks the 40th anniversary of the 1975 fall of Saigon, an event that marked the decisive defeat of the largest US military intervention since the Second World War.

Having been compelled to withdraw the last of its combat forces from Vietnam two years earlier, Washington watched helplessly as the puppet regime of Gen. Nguyen van Thieu and its 700,000-strong US-trained and US-armed South Vietnamese army collapsed virtually without a fight.

The images of the last US personnel fleeing the besieged city from the embassy roof aboard helicopters have come to symbolize a historic debacle for Washington’s foreign policy establishment and the US military, whose effects are felt to this day.

In Washington’s criminal war of aggression against Vietnam, a succession of administrations—from Kennedy to Johnson to Nixon—combined to wage a war that was near-genocidal in terms of the violence inflicted upon an entire population.

Occupying the country with, at its height, more than 536,000 American troops, the US military dropped some 15 million tons of munitions in an aerial campaign that saw entire areas of the country carpet-bombed. In addition, more than 20 million gallons of toxic chemicals were dumped onto the Southeast Asian country, turning large parts of it into a wasteland and leaving millions of Vietnamese, including babies still being born today, damaged by their effects.

In all, more than 3 million Vietnamese lost their lives as a result of a US intervention in which hideous atrocities, like the mass slaughter of over 500 My Lai villagers—women, infants, children and the elderly—became commonplace. Those responsible for planning and prosecuting this war, Democrats and Republicans alike, are guilty of the worst war crimes since the fall of Hitler’s Third Reich. None of them, of course, have ever been called to account.

The fall of Saigon represented a stunning victory of an oppressed people against the most powerful imperialist nation on the planet. However, for all the heroism and sacrifice of the Vietnamese people in 30 years of war, first against French colonialism and then US imperialism, there is an undeniable element of tragedy in the conditions that prevail four decades after their victory.

This immense struggle did not succeed in liberating Vietnam from its status as an oppressed former colonial country. Forty years after the fall of Saigon, Vietnam has become a cheap-labor platform for foreign-based transnational corporations seeking super profits from the exploitation of Vietnamese workers.

And, 40 years after the last US forces were driven from Vietnam, the American military is coming back, with Washington sending warships to the country and supplying its military with weaponry as part of the drive to align Vietnam with US imperialism’s “pivot to Asia.” Thus, having defeated US forces in one of the bloodiest wars in the region, Vietnam could become a pawn in the preparation of a potentially far more catastrophic US war—this time against a nuclear-armed China.

Recently, Washington partially lifted a ban on the sale or transfer of lethal weapons to Vietnam—in effect since the US defeat in 1975—in order to ship Hanoi weaponry intended for “maritime security purposes.” The aim is to ratchet up tensions with China over disputed islands in the South China Sea.

Washington is also trying to draw Hanoi into the Trans-Pacific Partnership (TPP), a proposed trading bloc designed to check China’s rise as the preeminent economic power in the region. The terms of the treaty are designed to force the dismantling of Vietnam’s state-owned enterprises, opening up a still larger share of the economy to exploitation by US capital.

While China is Vietnam’s largest trading partner, the US has become its largest export market.

The fate of the Vietnamese revolution stems from its isolation, which was itself fostered by the nationalist outlook of the Vietnamese leadership. Even more decisive in isolating the Vietnamese revolution, however, was the role of the Stalinist, social democratic and trade union leaderships, which worked deliberately to divert the working class from the path of social revolution in country after country during the same period —France in 1968, Italy in 1969, Chile in 1973, Portugal and Greece in 1974, Spain in 1975.

For its part, the Maoist regime in China acted to weaken and isolate Vietnam with its 1979 invasion of the country, carried out to punish Hanoi for ousting the blood-soaked regime of Pol Pot in Cambodia. The US, which also backed the Pol Pot regime against Vietnam, gave its support to China’s aggression, which cost the lives of 100,000 Vietnamese civilians and some 125,000 soldiers and militia members.

Traumatized by the Vietnam experience, America’s ruling layers spent decades attempting to overcome what became known as the “Vietnam syndrome,” a euphemism for the American people’s hostility to militarism in the aftermath of a war in which nearly 60,000 US troops lost their lives and many more returned physically and psychologically shattered.

Within the US itself, however, the leadership of the mass antiwar movement that emerged against the US intervention in Vietnam did everything in its power to isolate the struggle against war from the struggle against capitalism—under conditions of a massive strike wave and a series of urban rebellions among the most oppressed layers of the working class—and to subordinate this movement to the Democratic Party. In the aftermath of the war, these layers, together with the Democratic Party itself, turned very rapidly to the right.

This provided the American ruling class with political breathing space to recover from the devastating defeat in Vietnam and the discrediting of all its institutions, from the presidency on down. As a result, it was ultimately able to revive American militarism in an even more aggressive and predatory form and carry out a sustained offensive against the American working class.

Forty years after the defeat of US imperialism in Vietnam, the lessons of this experience remain decisive. The most central of these lessons is that the fight against imperialist war can be waged successfully only through the independent political mobilization of the working class in an international struggle to put an end to the capitalist system.