The long-awaited airing this past September on PBS of The Vietnam War, directed by Ken Burns and Lynn Novick, brought the sights, sounds, and whirlwind of emotions of the most divisive conflict in 20th century American history roaring back into the national conversation after a long hiatus. Reviewers have rightly praised the film for many things, especially its ideological evenhandedness and its careful attention to the experiences of America’s adversaries, both the handful of communists who were the chief architects of North Vietnam’s victory, and the millions of ordinary Vietnamese who served the revolutionary cause as soldiers, spies, or political cadres.

This is all to the good. For far too long, American books and films about Vietnam have presented “the enemy” as a shadowy, faceless figure, motivated by a repellent political credo. The haunting question that hovers over virtually every significant book written in English about Vietnam is, “How could the United States lose a war to a poor, agrarian nation like North Vietnam?” The Burns-Novick film obliquely suggests we take a look at a closely related, but nonetheless very different, question: How did the communists win?

It isn’t every day that David defeats Goliath. That Hanoi was able to frustrate America’s designs for South Vietnam for so long, and ultimately force the United States to withdraw, has to go down as one of the most astonishing feats in the history of warfare. How, then, can we understand this extraordinary event?

A good place to start is with the recognition that Hanoi’s strategists never imagined they could force an end to America’s involvement through battlefield victories, despite their rhetoric to the contrary. They could not hope to match the Americans’ military power. But they believed—correctly—that they were more than a match for the Americans and their allies in the realms of political power and organizational skill. In a civil war between people who had suffered from a century of colonial exploitation, political power—or as the communist propagandists used to say, “the power of the masses, directed by the party”—proved far more effective that the conventional military strength the Americans brought to bear against it.

Hanoi “dismissed the assumption that the principal and primary means test of success must be military combat,” observes former State Department officer Douglas Pike, one of the most perceptive American students of the revolutionary forces in Vietnam. “They realized . . . that it might be possible to achieve a change of war venue and determine its outcome away from the battlefield.”

The communists’ primary assets in their long war against the United States were, first, a distinctly Vietnamese variant of Mao’s highly flexible protracted war strategy, designed to wear down the American people’s will to fight, even as it permitted the buildup of a powerful conventional army in North Vietnam. The second asset was a remarkably dynamic and cohesive political organization within South Vietnam that exploited the many vulnerabilities of the U.S.-South Vietnamese partnership. That organization, the National Liberation Front, enjoyed wide support among the rural peasantry that comprised about 90 percent of South Vietnam’s population of 16 million.

Finally, the communists possessed—in historian Jeffery Record’s phrase—“a superior strategic grasp of the political and social dimensions of the struggle.” It could well be said, in fact, that the Americans were not so much outfought in Vietnam as outthought. As the commander in chief of communist military forces Vo Nguyen Giap often remarked, American military forces were superior to his own by virtually every measure, but the Americans’ strategic assessments of the nature of the war, of their own strengths and weaknesses and those of their adversaries, were markedly inferior to those of the Hanoi and the southern insurgency in directed from afar.

So if Hanoi’s regular, i.e., non-guerrilla, military forces weren’t fighting to defeat the Americans in major battles, what were they doing? They were meant to inflict sufficient casualties on the Americans to undermine the army’s morale, and support for the war at home. And they sought to keep the American combat forces busy in the hinterlands, away from the people in the villages who provided sustenance to all the military and political forces of the revolution.

While Gen. Westmoreland focused the tip of the mighty American spear at the People’s Army of Vietnam and the regular units of the Vietcong in search and destroy operations, the superbly disciplined political cadres and guerrillas of the NLF were conducting a vicious but largely successful campaign to gain and maintain control over most of the rural peasantry. Throughout 1966 and 1967, as both the United States and North Vietnam steadily expanded their commitment to the struggle, Westmoreland continued to seek an illusory “crossover point,” when U.S. forces would have killed so many enemy troops that North Vietnam could no longer afford to replace them on the battlefields of the south.

Meanwhile, Hanoi effectively integrated a cluster of political and military initiatives to build up the strength of the political infrastructure in the South, and chip away at support for the Americans and their Saigon allies in the countryside, in the United States, and the world at large. It was called dau tranh—loosely translated as “struggle movement.”

The essential concept of dau tranh, writes Pike, was “people as an instrument of war. The mystique surrounding it involved the organization, mobilization, and motivation of people ...Violence is necessary to it but not its essence. The goal is to seize power by disabling the society, using special means, i.e., assassination, propaganda, guerrilla warfare mixed with conventional military operations, chiefly organizational. In fact, organization is the great god of dau tranh strategy and counts for more than ideology or military tactics.”

“ Awash in corruption and intrigue, the government of South Vietnam made little effort to connect with the peasantry, or to address their myriad problems. ”

Throughout the countryside, the political cadres of the NLF surreptitiously enlisted vast numbers of peasants in “mass associations” of farmers, students, women, and urban workers, and engaged them in rigorous indoctrination classes, where they stressed a handful of key themes: The Americans were colonialists just like the French, but with more money and better weapons; they were there to rob the Vietnamese people of their land, and their freedom. The South Vietnamese politicians and generals were puppets of the Americans and cared nothing for the people’s welfare. Only the forces of the revolution had the dedication, patience, and wherewithal to oust the puppets and the Americans, reunite Vietnam, and deliver justice and a bright future to the masses.

All these motifs resonated with the yearnings of a long-exploited, colonized people. On the other hand, the regime in Saigon, peopled by a South Vietnamese elite with close ties to French culture and institutions, never put forward an appealing political platform. Awash in corruption and intrigue, the government of South Vietnam made little effort to connect with the peasantry, or to address their myriad problems. Neither the Army of the Republic of Vietnam nor its local defense forces were able to break the iron grip the NLF held over most of the villages. They were often defeated by the Communist guerrillas in combat, and never developed an effective method for supplanting the political cadres of the NLF with their own administrators.

The regular North Vietnamese and Vietcong forces may not have beaten the Americans in big unit battles, but they performed with great courage and skill in tens of thousands of small unit fights, and by no means did all those clashes result in American victories. Moreover, Communist forces as a whole—porters, construction workers, farmers, soldiers, Vietcong agents who worked on U.S. and South Vietnamese Army bases—were able to frustrate America’s crucial military initiatives. By continuously expanding and improving the Ho Chi Minh Trial—the main conduit for supplies and replacement troops from North Vietnam to the southern battlefields—and by deploying large numbers of troops in Cambodia and Laos, the North Vietnamese defeated the American effort to isolate the battlefield from 1965 to 1968. And there was no way to defeat the Southern insurgency unless the battlefield could be cordoned off from North Vietnamese support. Despite an ambitious and sustained air interdiction campaign by the U.S. Navy and Air Force to cut the Trail, the numbers of troops and tonnage of supplies brought into the South actually increased virtually every month between 1965 and 1967.

The audacious Tet Offensive of January 31, 1968, in which every major city, town, and many key military installations in South Vietnam came under simultaneous communist attack, was something of a tactical disaster for Hanoi and the NLF. They took as many as 45,000 casualties over two months of fighting and were driven off all their objectives. But Tet’s crucial objective wasn’t to gain and hold territory. Rather, it was to inflict a devastating blow on the American public and its government by exposing the bankruptcy of America’s strategy in a very dramatic fashion.

The bloody fighting in Saigon, and then the month-long savage fight by the U.S. Marines to take back the old imperial capital of Hue, put the lie to Gen. Westmoreland’s rosy assessment of November 1967, when he’d predicted that “we are reaching the point where the end is beginning to come into view.” Tet forced a searching re-examination of American policy and strategy in Washington. A new consensus emerged within the Johnson administration by the end of March: The United States couldn’t achieve a military victory at an acceptable cost. Negotiations offered the best path to peace. The burden of the fighting must be gradually turned over to the South Vietnamese, and America’s forces must be withdrawn.

For the United States, Tet “was a long-postponed confrontation with reality,” writes historian Gabriel Kolko. “It had been hypnotized until then by its own illusions, desires, and needs. The belated realization that it had military tactics and technology but not viable military strategy consistent with its domestic and international priorities made Tet the turning point in the [Johnson] administration’s calculations.”

After 1968, Hanoi declined to engage its regular forces in big battles and reverted almost entirely to small-unit guerrilla action for about two years. American ground forces began to withdraw in large numbers in mid-1969. Nixon expanded the war into Laos and Cambodia, killing tens of thousands but making no significant dent on Hanoi’s will to carry on until it reached its ultimate objective. North Vietnamese leaders Le Duan and Le Duc Tho, two of the toughest negotiators in the annals of diplomatic history, ultimately obtained an agreement guaranteeing the withdrawal of all U.S. forces from Vietnam by March 1973, while North Vietnamese units in South Vietnam were permitted to remain in place.

Richard Nixon claimed that “The Agreement on Ending the War and Restoring Peace in Vietnam” had achieved “peace with honor.” Historians have interpreted the document quite differently. America had extricated itself from a quagmire, but there was little doubt within the administration, or among close observers of the war outside of it, about what lay ahead for South Vietnam.

In January 1975, less than two years after the last U.S. combat troops left Vietnam, Hanoi mounted a massive 22-division armored invasion of South Vietnam. The Army of the Republic of Vietnam, with few spare parts and insufficient ammunition for its American helicopters, fighters, and heavy artillery, was no match against Hanoi’s formidable military machine. Nixon had resigned in disgrace the previous August, and President Gerald R. Ford and Congress had no intention of honoring his secret pledge to come to South Vietnam’s aid with American airpower.

On April 30, 1975, Saigon fell just a few hours after U.S. Marine helicopters flew the last Americans out of the city to Navy ships in the South China Sea.

A few days before the end came, Major Harry G. Summers, United States Army, said to his North Vietnamese counterpart on a small team in Hanoi negotiating the final exit of Americans from the country, “you know you never defeated us on the battlefield.” Col. Tu of the People’s Army of Vietnam responded, “That may be so, but it is also irrelevant.”

And so it was.