Ban Mak Mouen is a slum along the Thai-Cambodian border. One U.S. official who visited there was so appalled by its air of menace that he remembers thinking, "Mak Mouen is a Jonestown waiting to happen."

Tens of thousands of Cambodian refugees have been squatting in border encampments like Mak Mouen for months. It is a place of the utmost squalor. Thousands of small straw huts are crammed together, with no planning, no organization, on the edge of a dusty plain. This is the dry season, and a stream running through the camp contains only a foul-smelling slick of sewage.

There appears to be no concern for public health in the camp. Piles of rubbish, melon skins, chicken bones, beer bottles, empty tin cans, plastic bags lie everywhere.

Among the refuse, engulfing the camp like a cloud, are flies feeding off the garbage and the piles of human excrement with which it is mixed. A little girl squats to defecate: she is at once covered by a cloud of flies.

There is no running water and when the tanks filled daily by the Red Cross run dry -- daily -- people bathe and wash their clothes in the foul stream.

At least 60,000 Cambodians have crowded into this instant slum in recent months for one reason: food. They are the homeless survivors of a year of famine that has reduced their once prosperous and serene homeland to an international synonym for disaster and humanitarian concern.

The famine came on the heels of a decade marked by war, bloody revolution and foreign invasion -- successive waves of destruction that began exactly 10 years ago this week, when the neutralist Phnom Penh government was toppled by a military coup and the Vietnamese war spilled across Cambodia's border.

Cambodia today resembles a broken mirror. Many of its pieces are missing; others do not match. Even assembled, the jagged shards reflect different views, different appearances.

Places such as Mak Mouen exist because they are distribution points for international food aid. They are one part of the reality of the Cambodian tragedy today; the other parts are reflected in the thickly carpeted offices of international aid bureaucrats, in the war ministries of Hanoi and Peking, in American churches and synagogues where reflief money is collected, and at other points on the globe touched by the Cambodian crisis.

The story of how food came to Mak Mouen, what happened to it there, and what the ultimate fate of its residents means for the world lies at the heart of the tangle of international politics and conflict that have created, and still prolong, Cambodia's suffering.

Even the most basic population figure -- one that would reveal how many Cambodians have survived this Asian Holocaust -- is a matter of mystery and fierce dispute among humanitarians and politicians.

But two things are clear:

Famine threatened to extinguish the people of Cambodia last year, and is now -- after a period of abatement -- again threatening the survivors. The new threat can be averted only by increased international aid and significant improvement in the way the Vietnamese occupiers of Cambodia respond to the continuing crisis.

About 250,000 Cambodian refugees now in camps just inside Thailand or along the Thai-Cambodian border risk being forced back into the war zones of their homeland unless the rest of the world can find what is called "a durable solution" for them.

The famine has no natural causes -- Cambodia, unlike Bangladesh, is not a naturally impoverished land. The disaster was even foreseen. With an accuracy that is chilling in retrospect, a U.S. Agency for International Development team, in its final report upon leaving a collapsing Phnom Penh in April 1975, concluded:

"If ever a country needed to beat its swords into plowshares in a race to save itself from hunger, it is Cambodia . . . The prospects that it can or will do so are poor . . . Slave labor and starvation rations for half the nation's people will be a cruel necessity for this year and general deprivation and suffering will stretch over the next two or three years before Cambodia can get back to rice self-sufficiency."

The worst of these predictions, and more, came true. No matter how grim they thought their vision, the AID team members did not imagine the horrors that were to take place over the next five years and that continue today.

Cambodia's present predicament is confirmation that disasters, like fashions, have a short life in the popular attention that was gripped with anxiety over the plight of the Vietnamese boat people.

Only gradually, as television screens and newspapers in the early autumn became filled with the pictures of starving mothers and children, did the West become aware of the suffering Cambodia had endured for a decade. Hundreds of thousands of its people were surging in despair toward the Thai border, and reports from inside Cambodia spoke of a dreadful emptiness and desolation.

"Two million dead by Christmas" became a comon slogan for international and private relief agencies that began to mobilize their resources as donations flooded in.

The famine that the world became aware of so suddenly in 1979 had, in fact, been a decade in the making. Although new crises in Iran and Afghanistan have pulled public attention away, Cambodia remains at the brink of ultimate disaster.

This series will explore the past year of famine, and the complex political, military and humanitarian issues that it raised for Cambodia, for Cambodia's neighbors and for the international community.

Food paid for by American churches and synagogues collecting special offerings have helped feed the overthrown, but still resisting army of Khmer Rouge leader Pol Pot, as well as starving villagers. At the same time, evidence indicates that some food paid for by British schoolchildren who sold their toys for Cambodian relief has gone to sustain occupying Vietnamese forces.

Such circumstances invite questions as to how far the concern, the money and the programs have been effective in saving the lives of ordinary Cambodians. Such questions arouse heated disputes, however, not to mention propaganda barrages from all involved.

It now appears that the death toll before Christmas, while considerable, did not reach 2 million. But it is difficult to determine if that is because the original reports exaggerated the threat or because international aid averted it.

As soon as it came into public view, famine in Cambodia eclipsed similar past disasters in Biafra and Bangladesh as the instant synonym for starvation. The questions that surround it are political.

There were extensive reports of famine long before the reflief agencies responded. What were the reasons for their delay, which inevitably caused deaths? Was it because of pressure from Western governments -- particularly the United States -- that did not wish to help the Vietnamese-installed government headed by Heng Samrin? Or was the delay caused by Vietnamese refusal both to admit that the famine existed and to allow the world to help?

Similar arguments are raised over the question of the distribution of the food that now has arrived. Some foreign relief workers and Western journalists who have recently visited Phnom Penh tend to be optimistic at this point about the situation inside Cambodia. They say they have been able to travel widely with few restrictions. They have seen international food aid taken from the warehouses and distributed to the needy. Thirty pounds of rice per person per month are available in Combodia, they say.

But along the Thai-Cambodian border, where the international agencies also have been making rice available to Cambodians, the view is different. People come from the interior on oxcarts or bicycles to collect food. They complain that the Vietnamese are not allowing proper distribution of international aid. tIn some villages, they say, the monthly ration is one pound, not 30.

This "rice-across-the-border" feeding operation is sometimes seen in Hanoi and Phnom Penh as a U.S. weapon to "destabilize" Heng Samrin's government by acting as a magnet to draw people away from Phnom Penh and into border areas controlled by the remnants of the Khmer Rouge. The theory is that the United States is seeking revenge against Hanoi and playing the China card, joining Peking's support for Khmer Rouge -- whom President Carter denounced in 1978 as "the world's worst violators of human rights."

U.S. officials in Bangkok and along the border vehemently deny such charges. Their effort is to feed starving Cambodians, not to help the Khmer Rouge, they say. They maintain that the border feedup program has kept 1 million Cambodians alive for several months.

Sorting out these disputes and questions is important not only because the Cambodian tragedy is an extraordinary piece of history, but also because continued disruption of the planting and harvest cycles inside the country indicate that another serious food shortage is about to develop.

More international aid than ever will be needed. Unless conditions inside Cambodia can be brought back to something approaching normalcy, the threat of famine is likely to become an annual occurrence.

Before its decade of war and revolution began on March 18, 1970, with a coup by Gen. Lon Nol against neutralist Prince Norodom Sihanouk, Cambodia was a peaceful country of 7 million people that was not only selfsufficient in rice, but exported it.

Between 1970 and 1975, when the Vietnamese war spilled over into Cambodia and created Cambodia's civil war, the agricultural system was completely destroyed -- by fighting, by U.S. bombing and by subsequent labor shortages. About half of Cambodia's people fled the countryside and became refugees in the towns. Cambodia became almost totally dependent upon imports of American food aid.

That aid ended abruptly in April 1975, when the U.S.-backed government of Lon Nol was defeated by the communist Khmer Rouge -- a group that had barely existed when the fighting began.

One of the seemingly more rational priorities of the Khmer Rouge, after their 1975 victory, was the attempt to restore rice self-sufficiency.

For nearly four years, the Khmer Rouge drove the population, with still unbelievable ferocity, to reconstruct the agricultural system -- building dams, canals, reservoirs and dikes. Just how successful they were is still a matter of dispute: certainly the people never were given more than minimum rations.

No one knows how many pople died under the Khmer Rouge. Figures as high as 3 million have been widely quoted. Whatever the number, there is no doubt that their regime was brutal. And there is little doubt that the vast majority of the survivors were relieved when the Soviet-backed Vietnamese invaded in January 1979 to replace the Chinese-backed Khmer Rouge with their own client government under Khmer Rouge defector Heng Samrin.

But according to refugees reaching Thailand, the popularity of the Vietnamese and their Cambodian collaborators was short-lived. Within months, the fact that Vietnam had traditionally been an enemy of Cambodia loomed more important than that the Vietnamese had liberated Cambodia from the Khmer Rouge. Food was one of the principal reasons.

In Cambodia, rice production, like fighting, is seasonal, governed by the yearly monsoon rains that begin in late May and end just before Christmas. Just as the January-to-May dry season is the traditional time for military campaigns in Indochina, so is the rainy season the time for planting and harvesting. Cambodia's principal rainy season crop, planted in May and June and harvested at the end of the year normally provides 85 percent of the year's rice.

The 1978 harvest, planted under the Khmer Rouge, was expected to be plentiful. But it was disrupted by the Vietnamese invastion. When the Khmer Rouge fled Phnom Penh in January 1979, they took some rice stocks with them and destroyed others. In the chaos, the rest of the harvest was not properly gathered.

The most detailed study of what what happened inside Cambodia during 1979 has been made by a young academic from Cornell University, Stephen Heder. He has spent months on the Thai-Cambodian border, interviewing some 250 Cambodians of different social, political and geographical backgrounds.

Heder's study was funded by the State Department "with the clear understanding that [he] would be completely free to draw and express his own conclusions whether or not these were in agreement with the views of the U.S. cgovernment." Heder has never been a supporter of the U.S. role in Indochina; until he began his research he was sympathetic to the Khmer Rouge.

Heder's study suggests that month by month through 1979, relief over liberation gave way to disillusionment and even opposition to the Vietnamese. In addition to the scarcity, this process was influenced by the fact that the Vietnamese failed to create a very powerful Cambodian administration - though this was perhaps in part because so many cadres had been murdered by the Khmer Rouge.

After the January 1979 invasion the Vietnamese encouraged Cambodians to leave the work camps the Khmer Rouge had corralled them in and return to their traditional villages. This obviously was popular. But, together with the continued fighting between the Vietnamese and Khmer Rouge, it disrupted planting for the year.

Such food stores as existed, and were not seized by the Khmer Rouge, were often requisitioned by the Vietnamese or their allies, or removed by traveling Cambodians who needed to feed themselves en route home.

By early summer last year, the Vietnamese had established reasonable control over major road and river routes, as well as within the towns. But the agricultural system once more was in chaos. An attempt to reintroduce some collectivized farming in May did not work.

As food grew scarcer, a rationing system was imposed; inevitably, ordinary people did less well than soldiers or officials.

By the end of the summer, Heder believes, the majority of the people had decided that "when it came to organizing the feeding of the population, the Vietnamese were inferior" to the Khmer Rouge. Hundreds of thousands of people began to make for the Thai border.

By fall, Heder says, "it seemed highly unlikely that the Vietnamese could ever recover even the original support they had enjoyed" when they overthrew the Khmer Rouge.

This is not to say that the Khmer Rouge have become popular. Their armed strength now is said to be about 25,000 (no one knows exactly); the civilians they control, they control by force.

The speed of the Vietnamese invasion destroyed their preparations to withdraw into widely scattered resistance areas capable of supporting large numbers of civilians. They were, however, able to regroup into bases in both the northeast and the west of the country. Last spring, the Vietnamese mounted a second offensive on the western bases, causing a second chaotic evacuation.

A large number of the civilians fled into redouts in the Cardamom Mountains of the southwest where there was no food at all, and where disease, particularly cerebral malaria, was endemic. By late August, enormous numbers of people, perhaps half of those under Khmer Rouge control, are believed to have died in the hills.

Last September, the Vietnamese tried once more to destroy the vestiges of the Khmer Rouge. Once more they failed. The effect was to push additional tens of thousands of dying people across the border into Thailand. They arrived just as the international agencies began massive relief operations there and in Phnom Penh.