IYADH, Saudi Arabia, Dec. 21 ?In the last decade, as thousands of young Saudis left their country to wage Islamic holy war, Saudi leaders let them go, aware of the danger they might pose to the United States, but more focused on the danger they would pose at home.

At least four times in the last six years, Saudis who were trained or recruited in Afghanistan, Chechnya, Kosovo or Bosnia have been among the terrorists who carried out bombings of American targets ?in Saudi Arabia, Kenya, Tanzania and Yemen. But not until October, after the American military campaign in Afghanistan began, did Saudi Arabia detain young men trying to join that fight.

Until then, the Saudi royal family performed a diplomatic and political balancing act. Choosing accommodation over confrontation, the government shied away from a crackdown on militant clerics or their followers, a move that would have inflamed the religious right, the disaffected returnees from other wars and a growing number of unemployed.

It appears to have been a miscalculation of global proportions, Western diplomats now say. As they look back to examine the roots of the Sept. 11 attacks, officials in Saudi Arabia, Europe and the United States describe a similar pattern. In country after country, Al Qaeda's networks took hold, often with the knowledge of local intelligence and security agencies. But on the rare occasions that countries did address the terrorist threat, they chose to deal with it as a local issue rather than an interlocking global network.

The result: for Osama bin Laden's most audacious strike against the United States, Europe was his forward base, Saudi Arabia his pool of recruits, the United States a vulnerable target.

In interviews here, former senior Saudi officials said they had recognized the exodus of warriors as a source for concern, for the kingdom and its American ally. But they insisted that they thought the danger could be contained.

Only after Sept. 11 did Saudi Arabia cut diplomatic ties to the Taliban government of Afghanistan, which was spreading a fundamentalist form of Sunni Islam dear to the Saudis even as it forged ever closer ties with Al Qaeda. The Taliban were recognized by just three countries.

The severing of ties appears to have been belated. In the waning days of the Taliban and Al Qaeda in Afghanistan, a former Saudi official estimated this month that the number of Saudis there, as combatants, prisoners or casualties, probably numbered between 600 and 700, and possibly as many as 1,000.

As many as 25,000 Saudis received military training or experience abroad since 1979, according to estimates by royal Saudi intelligence.

Rather than prevent young Saudis from enlisting in military ventures abroad or silence the sheiks encouraging them, some officials say Saudi Arabia has mostly tried to deflect the problem outside its borders.

"The Saudis' policies made the world safer for Saudi Arabia and the Saudi regime," said Martin Indyk, an assistant secretary of state for Middle East policy during the Clinton administration, who has become a prominent critic of the Saudi strategy. "I don't think it was their intention to make it unsafe for the United States. But that was the actual, if unintended, consequence of buying off the opposition, and exporting both the troublemakers and their extremist ideology."

Saudi officials say that an aggressive effort to stop the flow of holy warriors or halt financial transfers to militant groups or address the sources of a drift toward radicalism might have only inflamed the sentiment of extremists who saw both the Saudi government and the United States as their targets.

"There was absolutely no way and no reason to stop them from going," said one former senior Saudi official. He said that his government had "of course" seen the jihadis, or holy warriors, as a major problem, and had tried to monitor their travels with help from foreign governments. But he insisted that the young Saudis would have found a way around any barriers that were imposed.

Although a blanket ban on travel is clearly not enforceable, Western officials say that the Saudi government could have made a greater effort to identify potential terrorists or jihadis and disrupted their travel plans. Since Sept. 11, for example, the Saudi government has discouraged travel ?especially those under suspicion ?to countries like Afghanistan.

Among 15 Saudi hijackers who helped to carry out the Sept. 11 attacks, American officials say, some came from this new generation of jihadis, apparently recruited while traveling. Others were apparently recruited in Saudi Arabia itself. But none appeared on any Saudi watchlist, an American official said.

A former American ambassador to Saudi Arabia said that the problems posed by an exodus that exposed young Saudis to further extremism and to members of Mr. bin Laden's Al Qaeda organization should have meant that the issue was addressed directly. But he said the United States had never pressed for Saudi action.

"Alarm bells should have rung," said Wyche Fowler Jr., the former ambassador, who served in Riyadh until the beginning of this year. "Someone should have said, wait a minute, we can't have people marching off to choose their own jihad, without examining the foreign policy and security repercussions."

Through its history, Saudi Arabia has always tried to balance contradictory goals, preserving ties to the United States and the West, its defender in the Persian Gulf war, while accommodating what most analysts view as a deeply conservative majority that sees those ties as alien and potentially harmful to Islamic interests.

The United States, meanwhile, has tried to balance its heavy dependence on Saudi oil ?it imports about 18 percent of its oil from the kingdom ?with concerns about radicalism within the country. It has been wary of undermining or questioning the Saudi royal family. On both sides of a crucial alliance, hesitation and caution long prevailed over the confrontation of difficult issues.

Until Sept. 11, the Saudi balancing act seemed to be acceptable. The participation of its citizens in the earlier attacks had not received much attention in the West. At home, an internal terrorist threat that had flared in 1995 and 1996 seemed to have been shut down.

But with the attacks of Sept. 11, American and some Saudi officials say, shortcomings in the Saudi approach have become clearer.

In one of two 90-minute interviews for this article, a former senior Saudi official acknowledged that his government might have underestimated the extent of the problem, but he said the full dimensions of the problem had become apparent only with hindsight.

"That there were people calling for jihad against America, well, bin Laden had been calling for that for the last three years," said the former Saudi official, who spoke on the condition of anonymity. "The call had been there, the declaration had been there. But the fact that we had people who were willing not only to heed that call, but to go against everything Islamic, that was unimaginable."

A Sheik's Influence: Young Saudis Intent on Becoming Martyrs

In a cramped office at the rear of Princess Zohra Mosque, Sheik Saleh al-Sadlaan is dispensing judgments that carry enormous weight. On this night, his callers in person and by phone line up for his rulings on countless matters Islamic, from divorce to fasting and prayer.

The hardest questions, he says, include some that have become among the most frequent. Is it time, young Saudis want to know, to wage jihad in the defense of the Muslims, whose suffering appears nightly on their television screens, from places like Chechnya and the Middle East.

"If he says go, we will go, because he is our sheik," declared a prayer caller, Abdul Hadi, 24. In fact, Sheik Sadlaan said he had spent years trying to persuade his best young Saudis to stay home. But his advice seems tinged with ambivalence.

"If he truly wants to defend Islam, that is one thing," he said. "If he just wants to be brave, that is something else." In the last few years, he said, young men have come to him "more often than I can say," ready to leave their lives as students behind, having set their sights on martyrdom.

A half-blind man of 61, Sheik Sadlaan is a professor at the kingdom's leading Islamic university and a religious adviser to a senior member of the royal family. What he says carries the weight of the ulemaa, Saudi Arabia's official religious establishment, and what he says, carefully, is that the king is his imam, and the king does not currently advise young men to march off to holy war.

But asked about other scholars, like Sheik Hamoud al-Shuaibi, who since Sept. 11 and the American retaliation have openly called for jihad against the United States, Sheik Sadlaan stops short of condemnation.

"He made a mistake, but it was not a major one, and it does not detract from his reputation," he said of Sheik Shuaibi, a former teacher.

Even the Saudi government is not known to have taken action against Sheik Shuaibi, despite his statements that those who support infidels, or unbelievers, should be considered unbelievers themselves, a statement that would seem perilously close to treason in Saudi Arabia, still home to more than 5,000 American troops.

Out of roughly 10,000 religious scholars in the kingdom, perhaps just 150 embrace such a radical view, according to American estimates. But among this group, only a handful is known to have been detained by Saudi authorities since Sept. 11, and in the videotape recently broadcast in the United States, Mr. bin Laden was eager to know how Saudi scholars had interpreted his actions.

"What is the stand of the mosques there?" Mr. bin Laden was heard to ask.

"Honestly, they are very positive," answered the visitor, identified by a senior Saudi official as Khaled al-Harbi, a veteran of conflicts in Afghanistan, Chechnya and Bosnia, who named several Saudi scholars as having spoken out in favor of Mr. bin Laden's campaign.

Even if only a small fraction of Saudi religious scholars are sympathetic to such causes, Sheik Sadlaan acknowledged that some Saudis saw their rulings as more credible than his own, because of his close ties to the government and the royal family. (The mosque is named for the mother of his patron, Prince Abdelaziz bin Fahd, a minister of state and the son of the king.)

In 9 cases in 10, the sheik estimated, juggling a visitor's questions with the demands of an insistent phone, he had persuaded young Saudis to set aside their dreams of jihad. But he wondered how often his advice made a real difference.

"If they don't like what I have to say," he said, "they'll go to some other scholar, who will tell them what they want to hear."

Bin Laden's Rise: An Early Glimpse of Militant Forces

Shortly after Iraqi forces invaded Kuwait in 1990, Osama bin Laden approached Prince Sultan bin Abdelaziz al-Saud, the Saudi defense minister, with an unusual proposition. Mr. bin Laden had recently returned from Afghanistan, heady with victory in the drive, backed by Saudi Arabia and the United States, to expel the Soviet occupiers.

As recounted by Prince Turki bin Faisal, then the Saudi intelligence chief, and by another Saudi official, the episode foreshadowed a worrying turn. Victorious in Afghanistan, Mr. bin Laden clearly craved more battles, and he no longer saw the United States as a partner, but as a threat and potential enemy to Islam.

Arriving with maps and many diagrams, Mr. bin Laden told Prince Sultan that the kingdom could avoid the indignity of allowing an army of American unbelievers to enter the kingdom, to repel Iraq from Kuwait. He could lead the fight himself, he said, at the head of an group of former mujahedeen that he said could number 100,000 men.

Prince Sultan had received Mr. bin Laden warmly, but he reminded him that the Iraqis had 4,000 tanks, according to one account.

"There are no caves in Kuwait," the prince is said to have noted. "You cannot fight them from the mountains and caves. What will you do when he lobs the missiles at you with chemical and biological weapons?"

Mr. bin Laden replied, "We fight him with faith."

The conversation ended soon afterward, and the proposal was left to rest. But Saudi officials now say that the episode offered an early glimpse of several of the forces the kingdom would spend the rest of the decade trying to contain.

One such force was represented by Saudi veterans of the Afghan war, at least 15,000 men who had helped to drive the Soviets from Afghanistan in the name of Islam. Many returned to ordinary lives, but others did not.

Some remained in exile abroad, enlisting in other conflicts, in places like Bosnia. Others were jailed by the Saudi government.

In one sign of concern, a person knowledgeable about the kingdom said, the Saudi interior ministry conducted extensive psychological profiling of 2,500 veterans in an effort to identify those who were a potential security threat.

A second force was Mr. bin Laden himself, who soon returned to Pakistan. As early as 1992, Prince Turki said, "We started receiving information that he was active in recruiting Saudis to go there, and that he was in cahoots, so to speak, with some very unsavory characters, from Egyptian Al Jihad to Algerian groups, people who espouse terror as a means to carry out political ends."

A third was anti-Americanism, which gave further ammunition to Mr. bin Laden's cause, particularly when American troops stayed behind in Saudi Arabia after the Persian Gulf war. Mr. bin Laden was only one among the critics who said that the presence of "infidel" forces, for the protection of the kingdom, showed that the ruling al-Saud family was no longer legitimate, since its responsibilities included the protection of Islam's holiest sites at Mecca and Medina.

At the same time, Saudi officials concede, the problem of internal discontent was intensifying for other reasons: a surging population, stagnant revenues that sent per capita income plunging and growing unemployment.

Some of that disenchantment prompted direct criticism of the Saudi government. Royal profligacy and corruption were increasingly seen as indefensible.

The response was evasive. For decades, a former senior Saudi official said, the Saudi approach has been "to argue, and then to co- opt, in a way, and to act as if crimes weren't committed unless there were actual calls for an uprising against the government."

In the case of Mr. bin Laden, who by 1992 had in fact called for a toppling of the government, the Saudis moved slowly. They stripped him of his citizenship in 1994. But their attitude still betrayed uncertainty: for several years they relied on emissaries from Mr. bin Laden's family in the hope they could persuade him to change, officials said.

Among a series of shocks that brought extremism to the kingdom, the first came in November 1995, with a bombing in Riyadh that killed 5 Americans and wounded 37. Within months, four Saudis had confessed to the crime, including one who had served in Afghanistan, saying they had been inspired by Mr. bin Laden's calls to oust the nonbelieving forces from the kingdom.

Then in June of 1996 came a second attack. The bombing of an air base in the eastern city of Al Khobar, killed 19 American airmen and wounded hundreds more. Mr. bin Laden was long suspected of involvement, but Saudi and American investigators ultimately discounted that theory, blaming Saudi Shiite Muslims with ties to Iran.

Mr. bin Laden declared war against the United States in 1996, and two years later, he announced the forging of his "Coalition Against Crusaders, Christians and Jews." Yet it was not until June 1998 that the Saudis sought his arrest.

On a trip to Afghanistan, Prince Turki won what he said had been agreement from Mullah Muhammad Omar to surrender Mr. bin Laden. Three months later, after the August 1998 bombings of the American embassies in Kenya and Tanzania, Mullah Omar reneged.

"We didn't leave any stone unturned," Prince Turki said in an interview of the effort to secure Mr. bin Laden's arrest. He said his government had maintained relations with the Taliban even afterward, despite the fact that Mr. bin Laden's group had been implicated in the August attacks, in order to "leave a door open" for a Taliban change of heart. In fact, it seems clear that Saudi ambivalence toward a movement close to its own Wahhabi interpretation of Islam persisted.

Some American experts did question whether the Saudi government was prepared to bring Mr. bin Laden back home, and face a potential backlash from his admirers. "I think there was a conscious idea among the Saudis that they would rather have Osama in the Hindu Kush than anywhere else," said F. Gregory Gause III, an expert on Saudi Arabia at the University of Vermont.

In the Kenya attack, the terrorists included Mohamed Rashed Daoud al-'Owhali, a Saudi who later confessed to being recruited in Afghanistan. In the next major terrorist attack, the bombing in Yemen of the destroyer Cole in October 2000, another Saudi, Tawfiq al-Atash, who lost a leg in Afghanistan, has been identified by American officials as a likely leader.

In response to these events, the Saudis stepped up their supply of intelligence to the United States on Mr. bin Laden and his Al Qaeda network, officials from both countries said.

George J. Tenet, the director of central intelligence, traveled four times to Saudi Arabia between 1996 and 2000; Mr. Fowler, the ambassador, worked closely but secretly with Bakr bin Laden, the dissident's elder brother, to shut down sources of Al Qaeda's financing.

At the same time, the Saudis stepped up their oversight of money transfers. But one problem persisted: the charities whose funds sometimes found their way into the hands of extremists included prominent members of the royal family on their boards.

With more conflicts involving Muslims breaking out in Bosnia, Chechnya and elsewhere, many Saudis reached deep into their wallet. Since 1992, one Saudi charity, the Al Haramin Foundation, has increased twentyfold in size, distributing hundreds of millions of dollars over those years to schools and refugee camps in what officials of the group say are strictly humanitarian missions.

American officials say this largesse has been prone to significant "leakage," with money channeled to extremist causes and terrorist groups.

"The Saudi government never intentionally funded terrorism; that's nonsense," argued a former State Department official with long service in the region. "But what you had was a really serious command and control problem."

Sharing Intelligence: Cautious Cooperation but Strained Ties

Almost every day since Sept. 11, an F.B.I. official based at United States Embassy in Riyadh has met with Saudi counterparts to discuss the investigation, regular, face-to- face encounters that both sides regard as a major development in intelligence-sharing between the two countries.

But the two sides still walk on eggshells, the Americans careful in their questions, and the Saudis guarded in their answers, American officials said. Even in the post-Sept. 11 meetings, one senior Bush administration official said, the Saudis "dribble out a morsel of insignificant information one day at a time."

There are reasons for such caution, Saudi and American officials say. The very idea of close ties between the home of Islam's holy sites and the West remains alien to many Saudis. Since the Persian Gulf war of 1991, the partnership has come under increasing strain, because of differences over Israel and Iraq, over the American troop presence, and over terrorism, on which American requests for cooperation have often been perceived as insensitive to Saudi sovereignty.

"The United States sometimes expects Saudi Arabia to do publicly what they are willing to do only privately," said David Mack, a former deputy assistant secretary of state who served during the early 1990's as the top American diplomat in Riyadh. "They do not by inclination like to talk about what they're doing, whether it's good or bad."

Still, some American officials say the United States has leaned much too far in the direction of deference, thus failing to avert terrorist attacks.

In the mid-1990's, one administration official recalled, the Saudis would not acknowledge the existence of a Shiite Muslim group called Saudi Hezbollah, which was later acknowledged by the Saudis to have been among those responsible for the 1996 bombing in Al Khobar. "They would take our request and promise to get back to us and never did," the official said.

On the issue of Saudis heading off to holy war, Mr. Fowler, the former ambassador, said: "I'm willing to acknowledge up front that we missed it. It's the kind of thing that with hindsight, I wish I had thought to raise."

Even on terrorist financing, Secretary of Defense Donald H. Rumsfeld said during a visit to the kingdom in September that he had not asked the Saudis to freeze the assets of people and groups linked to Mr. bin Laden, even though the United States had asked all countries to do so. He said at a news conference that such matters were being handled by others.

"We understand that each country is different," he said, "each country lives in a different neighborhood, has a different perspective and has different sensitivities and different practices, and we do not expect every nation on the face of the earth to be publicly engaged in every single activity the United States is.

Not infrequently, Saudi and American officials say, the tiptoeing results in miscommunication. This month, a delegation led by a senior State Department official arrived in Riyadh, the Saudi capital, to discuss the issue of terrorist financing, only to find that the kingdom's most senior princes were already in or on their way to Jidda, for their annual retreat in the last 10 days of Ramadan.

For their part, Saudi officials say they were angry that the United States has not shared in advance some of its investigative findings, including the recent videotape showing Mr. bin Laden and a Saudi visitor.

Scrambling to respond, some Saudi officials mistakenly identified the visitor as a Saudi cleric who, it turned out, was still in the kingdom.

A former Central Intelligence Agency official said that American deference and other constraints, including efforts by the Saudis to discourage efforts by American diplomats to mingle with ordinary people, had left the United States dangerously dependent on the Saudis for information that could affect American as well as Saudi security.

"It's not that there are divisions within the intelligence community about Saudi Arabia," said the official, Kenneth M. Pollack, who served on the National Security Council staff in the Clinton administration. "It's that the intelligence community doesn't know."

Undetected Danger: Hijackers Remain
Mystery to Saudis

Saudi officials have revealed next to nothing about the Sept. 11 hijackers. The official position is that even the theory that Saudi citizens were involved remains unproven. But in private, Saudi and American officials say the real mystery to the Saudi government is not whether Saudi citizens took part, but how so many of them were able to evade detection by the Saudi authorities.

"All names that have been mentioned in the incident," Prince Nayef, the interior minister, said in an interview, when asked what his government had learned about the Saudis named by the Americans as hijackers, "they do not have the capability to act in a professional way." The statement amounted to yet another denial of Saudi involvement in the Sept. 11 attacks.

To the Saudis, American officials say, the fact that the Saudis involved in the assaults were unknown to them was almost as startling as the attacks themselves.

In recent years, the mubahith, the Saudi equivalent of the Federal Bureau of Investigation, infiltrated Al Qaeda cells within the kingdom, while the monitoring of the Saudis fighting abroad was thought to have kept a handle on potential troublemakers.

American officials say it is now clear that Al Qaeda networks were more deeply entrenched in Saudi Arabia than either the United States or Saudi Arabia understood. But they also say the Saudis may have missed clues left by young men like Hani Hanjour, a reclusive, religious young Saudi who told his family that he was working as a pilot in the United Arab Emirates from 1997 to 2000, but never left a phone number, and is now suspected of having been in Afghanistan at least part of that time.

Among the Saudi hijackers, only two, including Khalid al-Midhar, ever turned up on the State Department's antiterrorist watchlists, American officials say, and not until after they entered the United States. They had been identified as suspicious, not by the Saudi authorities, but because they stopped in Malaysia to meet with Mr. Atash, the suspect in the Cole attack.

Some American officials say that the Saudis placed a higher premium on hounding potential troublemakers out of the kingdom than keeping tabs once they left.

"Isn't it better that they go off and fight a foreign jihad, rather than hang around the mosques without a job and cause trouble in Saudi Arabia?" said one such official, who spoke on the condition of anonymity in summing up what he called the Saudi view. "They've radicalized a group that wouldn't have been so radical had they stayed home."

At the Zohra mosque in Riyadh, Sheik Sadlaan said the end of Ramadan seemed like a good time for reflection. The news from Afghanistan had been disturbing, with the names of young Saudis killed in battle beginning to circulate around the kingdom, posted on Web sites but never mentioned in Saudi newspapers, which operate under close government supervision.

The dead included young men like Badr Muhammad al-Shubaneh, whose tearful relatives were telling callers that they still could not explain why the 22-year-old college freshman, a social studies student at King Fahd University in Riyadh, had abruptly left the kingdom a year ago, to end up killed in Afghanistan in the first week of December.

"It's a big problem," Sheik Sadlaan said of the zeal for jihad. "It will create problems for the country and beyond."

But with Muslims seen as under siege in so many places, he said, he could not imagine the militancy ending any time soon. "It's not just the Saudis," he said. "The strong desire to help and defend and fight for the Muslims ?it's felt all over the Arab world."