The head-banging theory of how Vietnam is run goes like this: Hanoi's aged, long-entrenched leadership is like a man banging his head against a wall. He does it relentlessly, day in and day out, knowing that one day the pain will cease. He knows the pain will cease, not because one day he will stop banging his head, but because eventually he will demolish the wall.

A western diplomat here used that analogy to illustrate his point that "Vietnam's outward-looking policy is one of constant confrontation." American scholar Douglas Pike calls it the doctrine of dau tranh, which literally means struggle but connotes something more complex.

To Hanoi's crusty leaders, dau tranh can be military, political or diplomatic struggle or a combination thereof, Pike says. It views time as an ally, and victory as inevitable.

"We know we'll win," says the Vietnamese mindset, according to the diplomat. "If it takes 100 or 1,000 years, we'll win."

This outlook has carried Hanoi's leaders through an almost uninterrupted state of war since World War II. It has served them well against the Japanese, the French and later the Americans, and it seems to frame the leadership's view of the current conflict with resistance guerrillas in Cambodia.

But some observers wonder whether its usefulness is now running out. The impatient Americans have been replaced as Hanoi's number one enemies by the Chinese, who think in even longer terms than the Vietnamese. And the value of dau tranh is questionable in dealing with the economic difficulties that beset the country.

In fact, it has become almost a cliche that Hanoi won the war, but failed to win the peace, that a leadership mired in 1920s-style Stalinism has shown itself incapable of running a modern economy.

Now there is a feeling among diplomats and scholars that some changes may be in the offing -- dictated not only by economic realities but by mortality.

The 13-member Politburo, in which the average age is 72, is believed to represent the longest-serving leadership of any country in the world. It is headed by Le Duan, 77, who holds the post of secretary general of the Vietnamese Communist Party. Even the party's 116-member Central Committee is not much younger, with an average age of about 69.

Vietnam-watchers are looking to a party congress likely to be held next year for signs of changes in the aging leadership. But no one outside the inner circle of Vietnamese leaders seems to know yet whether any significant changes will occur, whom they might involve or what they would bring.

There have been rumors that Premier Pham Van Dong, 78, the number three man in the party hierarchy who has held his government post since 1950, may be preparing to step down at the party congress because of ill health and fatigue. But major changes in the top leadership are generally considered unlikely -- barring death or disability -- although there may be some "rejuvenation" of the Central Committee's lower echelons with the introduction of some younger members.

"I don't think the top five leaders can be moved," said a European diplomat. "They're too important. I think they're going to die at their posts."

Besides Le Duan and Pham Van Dong, the others in the top five are Truong Chinh, 77, the party theoretician who ranks number two in the Politburo and serves as head of state; Pham Hung, who holds the powerful post of interior minister and ranks fourth in the party, and Le Duc Tho, 74, the former Paris peace negotiator who ranks fifth and holds no government post, but is believed to run the day-to-day affairs of the country.

It is the name of Le Duc Tho, the nemesis of U.S. former secretary of state Henry Kissinger, that comes up most often when Vietnam-watchers speculate about a successor to Le Duan. But one senior Central Committee member discounted this, hinting that he was too old and infirm.

In any case, diplomats and Vietnamese officials say, Le Duan has recovered from an earlier illness and seems much stronger this year than last, appearing last month at lengthy meetings and parades in Hue and Danang marking 10 years since those cities were "liberated" by Communist forces near the end of the Vietnam War.

Asked about the prospect of having to replace aged Vietnamese leaders, Hoang Tung, a member of the Communist Party secretariat, said that "we don't consider it a problem for us. If necessary, we can have a meeting immediately to decide on a new leader." 'Present at the Creation'

Vietnam-watchers generally agree that major leadership changes are practically a prerequisite if there is to be any progress toward solving the country's most onerous problems: its growing isolation, its six-year-old war in Cambodia and its state of hostilities with China.

According to Pike, a Vietnam scholar at the University of California at Berkeley, "the leadership has become calcified, characterized by rigid thinking and inflexibility in dealing with problems."

In a paper presented at a conference in Thailand in January, he added, "It has so isolated itself that it seems unable to acknowledge the cause, extent or sometimes even the existence of problems besetting the society. Each year the Hanoi political system becomes more of a gerontocracy."

"In many respects, this is the only serving Communist hierarchy which began at the beginning," said a western diplomat in Hanoi. "Three-fourths of the Politburo was there at the origin of the Indochinese Communist Party," founded by Ho Chi Minh in 1929 as the precursor of today's Vietnamese Communist Party. "Fifty-five years have gone by, and they're still there," he said.

"The rulers of Vietnam today are very largely the same small group present at the creation in 1945," when Ho Chi Minh proclaimed an independent government in Hanoi, Pike wrote. "There are 40-year political associations here, both political friends and political foes -- but even antipathy extending over four decades takes on the quality of a bond."

Some of the closest bonds may have been formed in prison during the 1930s, when the French colonial rulers of Vietnam arrested a number of Communist revolutionaries and banished them to underground cells and harsh conditions on the prison island of Poulo Condore off the southern Vietnamese coast. Among those jailed there were Pham Van Dong and Le Duc Tho.

However, details are sketchy on the backgrounds of many of the most prominent Vietnamese leaders.

So secretive is the world's oldest Communist old-boy network that several of the highest-ranking leaders are known to the public only by their wartime aliases. Le Duc Tho, for example, is a nom de guerre, and so is Truong Chinh, which means "long march" in Vietnamese and reflects a youthful infatuation with Mao Tse-tung's revolutionary feat.

In their penchant for pseudonyms, these leaders take after Ho Chi Minh, whose name is believed to have been Nguyen Sinh Cung when he was born in 1890. During his long career as an itinerant revolutionary, Ho used many pseudonyms -- the best known of which was Nguyen Ai Quoc, or Nguyen the Patriot -- before he settled on Ho Chi Minh, meaning "he who enlightens." Does Something Have to Give?

Since Ho's death in 1969, his disciples have carried on in his name with a remarkably cohesive collective leadership, one of the few in the world that have worked as such.

Now, however, Vietnam is approaching what Pike called "a generational transfer of power."

When that transfer comes, he wrote, "changes in policy seem certain."

Yet, some western diplomats in Hanoi feel, it may be too much to hope that the next generation of leaders will make any major departures from the line of the old men who now run the country.

The old leaders "took a lot of very courageous decisions in their lives," said one European ambassador. "I'm a little bit afraid of the younger generation, which has been brought up in this stifling system. They have not been encouraged to use their brains to act individually."

He said that the prospects for new courageous decisions "may diminish as the younger technicians and bureaucrats take over," adding, "It's in their vested interest to keep the system as it is."

Indeed, when all of Vietnam's many problems are considered -- its poverty, its isolation, its continuing war in Cambodia, its difficulty digesting the south, its fear of China -- on paper it looks like something has to give.

But when one watches Vietnam's peasants toiling in the rice fields as they have for centuries, stooped over planting or plowing with water buffalo, oblivious to everything else, it is easy to think as the oldest Vietnamese leaders probably do: that nothing has to give.