Abdullah bin Abdul Aziz, the sixth king of Saudi Arabia, has died at age 90, state television announced. A master politician, he gained a reputation as a reformer without changing his country’s power structure and maintained good relations with the United States while striking an independent course in foreign policy.

He had been treated for pneumonia at a hospital in Riyadh in recent days.

Combining an avuncular style with a reputation for honesty and a shrewd understanding of the media, King Abdullah was popular with his subjects, who found him a refreshing corrective to his corrupt and autocratic predecessor, King Fahd.

[View: The Saudi royal family tree]

King Abdullah pumped billions of dollars into modernization of the Saudi educational system, opened up the Saudi economy, ushered his country into the World Trade Organization, curbed the authority of the religious police, pardoned some victims of an unforgiving judiciary, met with then-Pope Benedict XVI and espoused interfaith tolerance, cracked down on extremism, reached out to women and offered a plan for Arab peace with Israel.

Yet the cumulative effect of his policies was to reinforce the House of Saud’s absolute power over the country. His embrace of reform did not extend to politics. Dissenters who went too far were jailed or silenced, though he did reinstitute elections for municipal councils and announced that women could vote and run as candidates in the next round.

His predecessor, Fahd, suffered a debilitating stroke in 1995. The following January Abdullah, as crown prince, assumed most of the duties and responsibilities of the monarch, and in effect ran the country as regent until Fahd’s death in 2005.

[Read: Abdullah death sets up complex succession process]

At the end of his reign, Saudi Arabia was a different country from the one in which he came to power — much more open to economic entrepreneurs, more receptive to public discussion of its many problems, and even courting tourists. But in another sense, the country was unchanged: All power ultimately lay with the royal family, supported by a compliant religious establishment, and ordinary citizens still were disenfranchised.

King Abdullah gained worldwide renown for his sponsorship of a new graduate-level university, named for him, in which classes and laboratory sessions are coeducational, a breach of taboo that heartened liberals across the country.

At the same time, he ordered the construction of an all-female university in Riyadh, perpetuating the gender segregation that has become perhaps the biggest obstacle to economic progress in Saudi Arabia. It was a typical move for a monarch who always sought to balance a new generation’s desire for change with the conservative establishment’s commitment to Saudi Arabia’s traditional ways.

[From the archive: Succession stirs controversy in Saudi Arabia]

Saudi Arabia's King Abdullah bin Abdul Aziz has died Friday, most likely at the age of 90, according to state television. His brother Crown Prince Salman will be his successor. (Reuters)

When human rights and social justice advocates sent King Abdullah a petition in the spring of 2003 seeking an elected parliament, term limits on princes holding government positions and public access to the trials of accused terrorists, most of the signers were jailed briefly, and the king granted none of their requests. After seven decades of al-Saud rule, it would have been astonishing if he had.

Monarch in title and practice

The country’s Basic Law of Government, promulgated by Fahd in 1992, stipulates that the country is a monarchy and that it is the duty of citizens to obey their king. The government did not waver from that mandate during King Abdullah’s years on the throne.

His reputation as a progressive and generally benign monarch lay in the creation of new institutions that appeared to empower the Saudi public, such as the forums of the National Dialogue and a government human rights commission that occasionally allowed people to sound off without actually challenging the king’s power.

On the contrary, the steps King Abdullah took to limit the power of the Muslim religious establishment and to institutionalize the process of royal succession, combined with the government’s relentless campaign against homegrown jihadists who began a campaign of domestic terrorism in 2003, left the House of Saud stronger than it was before he took the throne.

And inside the royal family, King Abdullah’s adroit maneuvering largely neutralized the dissatisfaction and resentment of powerful half-brothers who had been his rivals for power. He opposed the decision by Fahd and Prince Sultan bin Abdul Aziz, the powerful defense minister, to invite U.S. troops into Saudi Arabia after the 1990 Iraqi invasion of Kuwait, for example, but avoided a public breach that could have weakened the family.

Before King Abdullah, the greatest threats to the al-Saud regime were domestic: a rising tide of religious extremism supported by al-Qaeda; and a restive citizenry energized by global information networks and unhappy with domestic corruption.

By the time of his death, the only real threat in the short- to medium-term was the increasing hostility of Iran, Saudi Arabia’s rival for religious and strategic supremacy in the region.

On that front, King Abdullah protected his flank by shoring up his country’s long-standing alliance with the United States, badly frayed by the involvement of Saudi citizens in the Sept. 11, 2001, terrorist attacks, Saudi aversion to the pro-democracy agenda of President George W. Bush and King Abdullah’s public denunciation of the U.S. occupation of Iraq as “illegitimate.”

King Abdullah could not resolve the fundamental paradox of Saudi foreign policy — that the regime is dependent for its security on its alliance with a country viewed with disfavor by much of the population. But he obscured the problem by boosting relations with China, Russia and other countries outside the American sphere of influence and by mending fences with Arab groups and regimes that are in disfavor with Washington, in particular Syria and the Palestinian hardline group Hamas.

Under King Abdullah, Saudi Arabia strengthened its security cooperation with the United States, as the two countries reached agreement on a long-term U.S. commitment to train a new armed force to guard vital Saudi oil installations.

As a result, U.S. Ambassador James B. Smith could say with some justification in October 2009, shortly after taking up his post in Riyadh, that “the relationship between Saudi Arabia and the United States has never been stronger; it has also never been more multifaceted or important. The United States values greatly the cooperation we have had with Saudi Arabia on a wide range of issues.”

Those issues include terrorism inspired by Islamic extremism, which Saudi Arabia nurtured for years for domestic and international reasons. After the onset of terrorist bombings inside the kingdom in 2003, Abdullah, then the crown prince, and other senior members of the royal family realized that the monster they had helped create had turned against them, and their response was swift and firm.

By the time President George W. Bush left office in January 2009, senior officials of his administration had concluded that the Saudi regime was no longer part of the problem but part of the solution to this global threat.

Inside the kingdom, the jihadist uprising inspired mostly revulsion at the pointless deaths that were inflicted, mostly on Muslims, and the Saudi regime received strong popular support for its mass arrests of suspected extremists, its shootouts with terrorist cells and its campaign, inspired by King Abdullah, to convince young men that al-Qaeda’s vision of Islam was a deviation from Islam.

King Abdullah was perhaps best known to the world for his introduction of the so-called Abdullah Plan for Arab Peace With Israel, which he first floated in a 2002 conversation with New York Times columnist Thomas Friedman. That plan calls for a full peace between all Arab states and Israel if Israel returns to the borders that defined it before the 1967 war — that is, if Israel gives up the West Bank, the Golan Heights and East Jerusalem.

King Abdullah persuaded all countries of the Arab League to accept this formulation and then took the position that he had done all he could to advance the peace process, despite entreaties from Washington to do more. He rebuffed a request from President Obama to make further goodwill gestures toward Israel, such as permitting airline overflights, in an effort to get peace talks resumed.

King Abdullah, whose official title was Custodian of the Two Holy Mosques, was also prime minister, as is customary in the Saudi system. Domestically, he pumped billions of dollars into new industries and the creation of new cities, but his most enduring legacy besides the coed university may turn out to be the institution known as the Allegiance Council, which he created to resolve uncertainties about the line of succession.

The council consists of 35 senior princes, all sons or grandsons of the first king, Abdul Aziz ibn Saud, who are to meet in secret each time a king dies or is incapacitated to choose the next in line, much as the cardinals of the Catholic Church elect a pope.

If the Allegiance Council had existed in earlier decades, it is doubtful that King Abdullah would have become king, because he was never fully in harmony with the powerful clique of princes known as the “Sudairi Seven,” all sons of Abdul Aziz and his favorite wife, Hassa bint Ahmed al-Sudairi.

Fahd was one of the seven, as were the late Prince Sultan, a former minister of defense, and the late Prince Nayef, a former interior minister. King Abdullah had a different mother.

Not one of his father’s favorites

Little is known about King Abdullah’s early life. He was born in Riyadh, then a mud-walled desert outpost, probably in 1924, the 13th of 45 known sons of Abdul Aziz. Unlike his half-brothers Saud and Faisal, who were sent to Europe as teenagers to prepare them for eventual rule, Prince Abdullah was not one of his father’s favorites.

He had little formal education, although he became an avid reader in later life and an advocate of libraries. As a young man, he was mayor of Mecca.

In 1962, after a power struggle among the princes, he became commander of the National Guard, a Bedouin-based domestic peacekeeping army. The National Guard, trained and equipped by Americans after 1975, remained his power base for the rest of his life.

Faisal was assassinated in 1975, and his weak and ineffectual successor, King Khaled, appointed Prince Abdullah second deputy prime minister, behind Fahd, the crown prince and heir apparent. Prince Abdullah became crown prince when Fahd succeeded Khaled in 1982.

Fahd and his crown prince were more rivals than partners, but as writer Mark Weston put it in his book “Prophets and Princes,” Fahd “had no choice but to appoint Abdullah crown price. . . . If Fahd had passed over Abdullah and appointed his full brother Sultan as crown prince instead, he would have infuriated not only the clergy, who preferred Abdullah, but everyone in the royal family who was not a Sudairi.”

King Abdullah is believed to have had at least seven wives during his long life and has four surviving sons, including Miteb, who succeeded his father as commander of the National Guard. He is also said to have had 15 daughters.

Lippman is a former Washington Post foreign correspondent.