King Fahd bin Abdul Aziz of Saudi Arabia, who died yesterday in Riyadh, probably at 84, was the mastermind behind the modernization of his desert kingdom; but by allowing American forces into his country in 1990 he provoked the hatred of Osama bin Laden, the world’s most dangerous terrorist.

After decades of an indulgent and unhealthy lifestyle punctuated by periods of hard work, Fahd suffered a debilitating stroke in 1995, withdrawing from public life three years later, and nominating as his successor his half-brother, Crown Prince Abdullah.

As one of the world’s last absolute monarchs, the 11th son of the kingdom’s founder, bin Saud, often found it difficult to project himself as a man with the soul of a Bedouin. More of a city dweller, Fahd, the fifth ruler of his country since 1932, took pride in his status as custodian of the Two Holy Shrines of Medina and Mecca, the most sacred places in Islam.

The biggest crisis of his reign came in August 1990, when Iraq invaded Kuwait. Under pressure from Washington, Fahd persuaded reluctant senior Saudi clerics to sanction the stationing of Western forces on his territory. But the arrival of American and British troops under General Norman Schwarzkopf opened bitter wounds in the Muslim world dating back to the Crusades.

Repeatedly using language that evoked images of the medieval holy war against Islam, Mr. bin Laden, the Saudi-born leader of the terrorist movement Al Qaeda, asserted that Fahd had “sided with Jews and Christians” and committed “an unforgivable sin.” Although Mr. bin Laden initially directed his anger toward America rather than the House of Saud, his secondary intention became the destruction of the Saudi royal elite, in order to turn Saudi Arabia into an Islamic theocracy.

Under Fahd, Saudi Arabia walked a difficult balancing act. In the West, the kingdom proudly paraded its alliance with the United States and its balanced policy on oil pricing as a sign of stability. On the Arab street, Fahd downplayed the links with Washington and tried to promote Islamic piety and defense of the holy places. The alienation of Mr. bin Laden and his followers, who went on to provoke America again with the September 11 atrocities, gave Fahd’s successors a tricky hand to play, especially after terrorists repeatedly struck in Saudi Arabia itself as Fahd lay incapacitated on a life-support machine.

As crown prince under his elder half-brother King Khalid, Fahd had presided over a country whose oil reserves produced riches so great that they were capable of undermining the Western economy. But he had the misfortune to become king in 1982, as Saudi Arabia’s oil bonanza was coming to an end, due to a collapse in the world price of oil, and as Islamic extremism was becoming an increasingly destabilizing force in the Middle East.

Instinctively averse to confrontation, he strove to keep his country out of direct involvement in Middle Eastern conflicts. However, he found it more and more difficult to walk the tightrope between maintaining cordial relations with the West and retaining Saudi Arabia’s independent status in the Islamic world.

He responded to the growing threat of Islamic extremism with repressive application of Islamic sharia law and strict censorship – policies that earned him the opprobrium of international human rights organizations and seemed at odds with his early reputation as a reformer.

Yet they served their purpose in quelling dissent and legitimizing the monarchy in Arab eyes. After the 1990-91 Gulf War, many predicted the imminent demise of the Saud dynasty. That these predictions proved premature owed much to the unique blend of piety and indulgence, development and constraint, Islamic orthodoxy and rampant capitalism that marked King Fahd’s regime.

Fahd bin Abdul Aziz Al Saud is thought to have been born in 1921, the 11th of 43 sons of bin Saud, who united the kingdom by conquest during the 1920s and became the first king of the new state of Saudi Arabia in 1932.

Fahd’s power base as king would be rooted in his close alliance with his full brothers and sisters, the sons and daughters of Hassa Sudairi by her second marriage to the king. Before his mother died in 1969, Fahd and his six brothers – known as the “Sudairi Seven” – would go every day for lunch at her house. The extended family continued to meet once a week whenever possible, and their cohesion later enabled Fahd and his brothers to overcome a number of serious security crises, in particular the siege of the Grand Mosque in Mecca by Islamic fanatics in 1979.

As a boy, Fahd received a traditional, but limited, court education in religion, hawking, chivalry, and politics. Like many of his fellow Saudi princes, he led a dissolute life as a young man and became a familiar figure at casinos along the French Riviera. He was superstitious, and disliked going to his capital, Riyadh, because a fortune-teller told him that he would die there.

In the spring of 1953 he was appointed minister of education, a role in which he pursued the cause of schooling for women. He was part of the family group that pressed for the abdication in 1958 of his brother, the wastrel King Saud, in favor of the worthier Faisal.

Four years later, Fahd was given the key post of minister of the interior, and presided over the drafting of the kingdom’s first five-year plan. In the mid-1960s, he began a program of self-education, working his way through a reading list that included the works of Winston Churchill, whom he greatly admired, as well as the speeches of Presidents Kennedy and Johnson.

With his progressive views and pro-American leanings, he arranged personal briefings with bankers and economists, and began to form a vision of Saudi Arabia in which ordinary Saudis led the economy, not from behind padded desks but in small factories, trucking companies, fast-food chains, and small shops.

As second deputy premier from 1967, Fahd took part in devising oil investment policies, represented the king at conferences, and controlled the royal bodyguard. He also created a program for training Saudi technicians in the West, so that they could become responsible for the development of new industries in Saudi Arabia.

Throughout these early years he continued to indulge his taste for gambling. But in 1974, after a series of spectacular losses on the French Riviera, he received a severe reprimand from his brother, King Faisal, and thereafter mended his ways. His first real step toward the throne came in March 1975, when Faisal was assassinated by a deranged nephew. In the aftermath of the murder, a caucus of Saudi princes obtained approval from the ulama (religious scholars) for the succession of Khalid bin Abdul Aziz, with Fahd as crown prince and first deputy prime minister.

During Khalid’s reign, which lasted until his death in June 1982, Fahd was the real power behind the throne. They were halcyon days for Saudi Arabia: Oil revenue flooded in; the 5,000 princes in the royal family took their cut, and many, including Prince Fahd, became absurdly rich. Cadillacs, it was said, would be dumped in the desert when their ashtrays were full.

It was also a time of massive development. Under Fahd, the desert bloomed with cities of breathtaking architecture, with airports, conference centers, and broad highways, hospitals, schools, universities, and a new industrial sector. The most lasting monuments to Fahd’s success are the twin industrial cities of Jubail, on the Gulf, and Yanbu, on the Red Sea, which he nurtured as crown prince and saw come to maturity as king.

Despite his dominant position as crown prince, Fahd observed diplomatic courtesies, always deferring to his brother in public. In 1981 Margaret Thatcher, then prime minister, came away unimpressed from a meeting with King Khalid and Crown Prince Fahd: “Fahd didn’t have a word to say,” she said. But it was pointed out to her that Fahd had not wanted to upstage his elder brother. It was during Khalid’s reign that the Saud family began to move closer toward religious orthodoxy. The seizure of the Grand Mosque by Sunni Muslim extremists in 1979, and sympathy demonstrations by Shiite extremists in the Eastern Province, resulted in the execution of 63 rebels in eight different towns. Segregation of women became more severe after the execution of Princess Mishaal for adultery.

In response to the discontent demonstrated by these disturbances, Prince Fahd announced in early 1980 that a consultative assembly (Majlis al-Shura) would be formed to act as an advisory body, and, following his accession two years later, he continued to talk of political reform.

But for a decade Fahd did nothing to fulfil these promises and continued to respond to growing instability in the region by yielding to pressure to pursue repressive social policies that seemed at odds with his reforming approach as crown prince. Saudi men were warned in a broadcast that they risked losing citizenship if they married foreign women. Every city had its own “chop square,” where murderers were routinely beheaded.

In 1986, Fahd adopted the title of “Custodian of the Two Holy Mosques,” dropping the style of “His Majesty.” It was intended as a sign of the Saud family’s commitment to Islam, which he subsequently cemented with a multibillion-dollar redevelopment program for Medina and Mecca.

While providing generous financial support for the PLO, Fahd played a leading role in attempts to solve the Arab-Israeli conflict. In 1981, as crown prince, he announced an eight-point plan for the settlement of the conflict that implicitly recognized Israel as an independent state.

The so-called “Fahd Plan” later formed the basis of an agreed proposal for the achievement of peace in the Middle East. His recognition of Egypt in 1987 was a bilateral decision unpopular with other Arab states that had severed diplomatic relations with Egypt in 1979, following the signing of the Camp David Accords.

Fahd made frequent visits to Washington and enjoyed good relations with Presidents Carter and Reagan. During the early 1980s, the Americans backed Saudi Arabia with military assistance, including Boeing AWACS surveillance aircraft. However, in 1988, after it was revealed that Saudi Arabia had bought medium-range missiles from China, the American Congress refused to sanction an agreement to provide further equipment; after that, Britain superseded America as the main source of military equipment.

But as time went on, Fahd found it increasingly difficult to juggle his allegiances and keep Saudi Arabia on the sidelines of Middle Eastern conflicts. During the Iran-Iraq war of 1980-88, terrified of the threat from Islamic fundamentalists in Iran, Fahd provided generous financial backing to Saddam Hussein, and, in 1989, signed a pact of non-aggression with him.

The deaths in Mecca, in 1987, of 403 people in riots instigated by Iranian pilgrims led the next year to diplomatic relations with Tehran being severed altogether. But in 1990, when Saddam turned his military might on Kuwait and proceeded to deploy armed forces along the Kuwaiti-Saudi border, Fahd came to regret his earlier support for Iraq.

At first he tried to put together a united Arab response. When this failed, he was forced to take the gamble of calling in the West to Saudi Arabia’s aid. The West’s rescue mission in the Gulf War of 1990-91 struck a deep blow to an economy already weakened by nearly a decade of low oil prices; it cost Saudi Arabia nearly $71 billion and demonstrated that the 30% or more of the budget devoted to defense was money uselessly spent.

But worse still in Arab eyes, and those of the terrorists allied with Mr. bin Laden, was the humiliating spectacle of the self-proclaimed custodian of the Two Holy Mosques calling in an army of infidels to protect Islam’s holy places.

The war was followed by a sharp economic downturn and a further collapse in international oil prices, forcing deep cuts in government spending. Billions of dollars in debt accumulated and arrears to foreign contractors built up.

Despite the need for austerity, Fahd continued to spend money on palaces in Geneva, Marbella, and elsewhere. In the 1980s, he and his entourage spent up to $4 million a day on visits to the palace at Marbella. On a private holiday, his fleet comprised up to eight aircraft, 400 retainers, 200 tons of luggage, and 25 limousines. In Riyadh, Fahd built a palace modeled on the White House but never lived there because of the political repercussions of imitating the American president. During the decade to 1993, Saudi per capita income fell to $6,000 from $14,000. The war and economic crisis energized political unrest, and during the early 1990s Saudi Arabia’s politicized middle-class moderates came together with a young generation of ultra-fundamentalists to demand political change.

In May 1993, the Saudi authorities disbanded a recently formed Committee for the Defense of Legitimate Rights, established by a group of six prominent Islamist scholars and lawyers. The group was re-formed in exile in Britain, from where it attempted to undermine the regime by publicizing its political crimes, corruption, and dismal human rights record, flooding the country with faxed newsletters.

Growing fundamentalist opposition culminated in November 1995 with the bombing of the Saudi National Guard Headquarters in Riyadh, followed in 1996 by the bombing of an American air force compound in Dhahran, which left 19 Americans dead.

Fahd responded to the unrest with a characteristic combination of extreme ruthlessness in stamping out fundamentalist dissent and measures to mitigate discontent among the merchant class. In 1993 he had responded to demands for reform by introducing a raft of constitutional changes, including the long-promised consultative council – with members appointed by the king.

Meanwhile, an increase in the number of executions in Saudi Arabia coinciding with strict enforcement of the Saudi residency law – which resulted in the expulsion of more than 100,000 illegal immigrants in two months of 1995 – demonstrated his determination to suppress unrest, provoking international condemnation.

In earlier years, Fahd had been capable of working all hours, but in his later years he was plagued by illness and senility. A heavy smoker, and overweight for most of his life, in his 60s he suffered from severe diabetes and arthritis and became prone, during important meetings, to relapse into long rambling speeches about his arthritic knees. From the mid-1990s onward, the reins of government were effectively assumed by his half-brother and heir, Crown Prince Abdullah.

King Fahd had three wives, one of whom predeceased him. He is also survived by seven sons and several daughters. The most prominent of his sons is Prince Abdul Aziz bin Fahd, born in 1971 to Muna Ibrahim. Crown Prince Abdullah has been named as Fahd’s successor.