As the leader of a conservative family dynasty of tremendous wealth and extraordinary power, King Abdullah ibn Abdulaziz al Saud was charged with steering the desert kingdom of Saudi Arabia through an unprecedented period of cultural upheaval, regional strife and economic challenge.
He had formally taken power in 2005, but had in effect been running the country for a decade before that, guiding it uneasily through the challenges posed by the Sept. 11 attacks in the United States, the war in neighboring Iraq, the disintegration of Syria, the upheavals of the "Arab Spring," and the rise of Islamic State.
Abdullah died Friday, Saudi state television reported, even as his state faced a new challenge in the meltdown of another neighbor, Yemen. He was 90.
His 79-year-old half brother, Prince Salman, is expected to succeed him.
An official Saudi statement, posted on Twitter, cited Salman as announcing "with deep sorrow" that Abdullah had died after a short illness. No other details were given, but Abdullah had reportedly been in ill health in recent weeks.
Heading one of the world's most strategically delicate nations at a time when the Middle East convulsed with upheaval and violence, Abdullah attempted to steer Saudi Arabia in an often ill-defined middle direction among conflicting pressures: its relationship with America and domestic demand for independence; the corrupting influence of massive oil wealth amid the enforced austerity of the kingdom's Wahhabism; and the homegrown social ferment of hard-line religious zealots and eager reformers.
President Obama paid tribute to the king, and homage to the alliance between the two countries, in a statement Thursday that spoke of the two men's "genuine and warm friendship."
"As a leader, he was always candid and had the courage of his convictions," Obama said. "One of those convictions was his steadfast and passionate belief in the importance of the U.S.-Saudi relationship as a force for stability and security in the Middle East and beyond."
Former President George H.W. Bush, who nurtured a close relationship with the Saudi royal family, issued a statement remembering Abdullah as "my dear friend and partner," and recalling the alliance the two helped forge in the Persian Gulf War against Saddam Hussein's Iraq, "a moment of unparalleled cooperation between two great nations."
Prayers in memory of Abdullah were scheduled for Friday afternoon at Imam Turki Bin Abdullah Grand Mosque in Riyadh. Citizens are due to pay allegiance to the new king and heir apparent after evening prayers Friday.
Born in the Saudi capital of Riyadh in 1924, Abdullah was one of more than 30 sons born to Abdulaziz ibn Saud, who founded the modern Saudi state in 1932. In the early years of the 20th century, the man known as Ibn Saud overcame rival tribes and fought off the Ottomans to unify a stretch of earth that would soon prove to contain oil wealth beyond dreams.
Abdullah was the product of the bitter tribal fault lines that cracked the kingdom in its founding days. His father was the venerated conquering hero; his mother was a bride claimed from one of the conquered tribes.
The young Abdullah, educated by a mix of Islamic scholars and military training, also spent years living in the desert with Bedouin tribes, according to his official biography.
He rose to command the kingdom's National Guard, an institution that long served as his seat of power in the bitter and largely hidden power struggles waged among the feuding scions of the House of Saud.
In 2005, the death of King Fahd cleared the way for Abdullah to ascend to the throne. But Abdullah had already been the de facto ruler of Saudi Arabia for a decade, since Fahd was incapacitated by a stroke.
His challenges were many. The attacks of Sept. 11, 2001, had badly dented friendly relations between the United States and Saudi Arabia, which regards itself as the de facto guardian of the interests of Sunni Muslims.
Subsequent American-led wars in Afghanistan and neighboring Iraq stirred Saudi hearts and raised fear of sectarian imbalance. The Israeli-Palestinian conflict raged on. Worries over a potentially nuclear-armed Iran shadowed Riyadh. And, meanwhile, rising world powers such as China came calling, courting Saudi Arabia for its vast oil resources.
At home, Abdullah contended with intense social pressures of a poorly educated, disaffected and massive youth population; women who languished with few rights or freedoms; poverty in the shadow of oil opulence; and the continuing struggle between conservative clerical thought and the thirst for greater freedom.
The Saudi-American friendship, founded on a decades-old codependence of oil and strategic necessity, took a bad hit with the 2001 terrorist attacks on the U.S. Fifteen of the 19 men who carried out the attacks were Saudi citizens, a fact that pushed many Americans to take a more critical look at the depth and quality of Riyadh's friendship.
Ties were further strained by the U.S.-led invasion of Iraq. Saudi Arabia has long feared that the war destabilized the region by giving too much political power to Iraq's Shiites, while simultaneously strengthening the hand of Shiite Iran.
Despite gnawing anxiety over growing Shiite power, Abdullah publicly touted improved ties with Iran for a time. But leaked diplomatic cables released by the WikiLeaks website in 2010 showed that, behind closed doors, Abdullah lobbied hard for the United States to "cut off the head of the snake" by attacking Iran's nuclear program.
Moreover, the civil war in Syria became something of a proxy war between Iran, the close ally of the embattled President Bashar Assad, and Saudi Arabia, which supported some of the rebel groups trying to oust him.
In recent weeks, Abdullah was presented with a new challenge as mostly Shiite Houthi rebels, believed to be supported by Iran, effectively took control of Yemen, which shares a roughly 1,000-mile border with Saudi Arabia.
As the powerhouse behind the OPEC oil cartel, Saudi Arabia under the leadership of Abdullah kept firm control over global oil prices, and was believed responsible, in part, for the recent sharp price dip that caused some economic pain to his country while harshly punishing the economies of Iran and Russia. It also, of course, brought relief to gasoline consumers worldwide.
Meanwhile, the Israeli-Palestinian conflict remained a festering source of tension, both in the Arab region and in the U.S.-Saudi relationship.
In 2002, Abdullah unveiled a plan for peace between Israel and the Palestinians. The proposed deal included full Arab recognition of the state of Israel in exchange for Israeli withdrawal to the 1967 borders.
The Saudi ruler was reportedly offended by what he regarded as a tepid American response to the initiative, which was largely ignored or discounted outside the Arab world.
Over the years, Abdullah gained a reputation as a moderate reformer, a leader who guided Saudi Arabia into the World Trade Organization and began to address some of the kingdom's most intransigent social troubles.
But his strokes of reform were tentative, and the basic orientation of Saudi society remained largely unchanged during his rule.
There was the election that allowed Saudi men to vote for just half of the representatives on relatively powerless municipal councils.
Abdullah's time also saw the much-touted appointment of the kingdom's first female minister to oversee the education of girls, even as Saudi women continued to be forbidden to drive, traveling without permission from a male guardian and a slew of rights that are regarded throughout much of the world as basic to all humans.
For ordinary Saudis, the years under Abdullah left no doubt that the kingdom's fundamental power structure remained unshaken and seemingly unmovable.
Abdullah is reported to have married as many as 30 women over the course of his lifetime, and is believed to have fathered dozens of children.
Stack is a former Times staff writer. Special correspondent Sherif Tarek contributed from Cairo.