As he takes over in Saudi Arabia, King Salman faces a list of foreign policy challenges that rival any a Saudi ruler has grappled with in decades.

To the immediate south, the government of impoverished Yemen collapsed even as the previous monarch lay dying. To the north, Saudi Arabia’s effort to overthrow President Bashar Assad of Syria instead helped create a menacing spillover, with fighters from the extremist Islamic State recently carrying out a bloody suicide bombing on the Saudi border with Iraq.

To the west, an old ally Egypt, once wobbling toward chaos, appears to be stabilizing under a new military regime, not least due to Saudi financial support estimated at $12 billion.

Most important, to the east, Iran looms as an ever-larger threat. The Islamic Republic has been steadily expanding its influence within the Shiite Muslim crescent from the Persian Gulf to the Mediterranean, and seems on the verge of repairing its abysmal relations with the West if it can conclude a deal over its disputed nuclear program.

The late King Abdullah made aggressive, often uncharacteristically open foreign policy moves to influence events in each of those arenas, particularly in the past two months when the kingdom forced world oil prices down by half. That and other Saudi foreign policy efforts since 2011 have all had one aim: to try to restore the old, autocratic order in the Middle East after a series of popular uprisings pushed one Arab country after another into chaos.

The death of a monarch will not alter that goal.

"The recent shift in Saudi regional and foreign relations is not how outspoken it has become, but how muscular it has become," said Fawaz A. Gerges, a professor of international relations at the London School of Economics. "It has long prided itself on acting behind the scenes."

The chain of events in the Middle East pushed Saudi Arabia into the open, particularly as the generation of post-colonial, dictatorial governments that had survived for decades tumbled one after another — first Iraq, then Tunisia, Egypt and Libya, while Syria erupted in flames. It has spent an estimated $25 billion trying to turn back political change.

President Saddam Hussein of Iraq, who helped keep Iran in check, fell to the U.S. invasion in 2003. President Hosni Mubarak of Egypt, who like the Saudis valued stability over change, was driven from office in 2011. Syria, once a stalwart ally, was drawn into Iran’s orbit as Assad relied heavily on Tehran, Iran, to put down a popular uprising. On the Arabian Peninsula, Riyadh, Saudi Arabia’s capital, felt compelled to dispatch its military to help suppress a Shiite uprising in Bahrain.

Saudi Arabia felt exposed, especially because many of the region’s revolutions brought to power the Muslim Brotherhood, and in Syria fueled the rise of the Islamic State, which declared its goal of establishing a Muslim caliphate. Both struck at the ruling Saud dynasty’s claim of being the sole embodiment of Sunni Islamic rule.

"The Saudis are trying to reassert the state system in the region," said Eugene L. Rogan, the director of the Middle East Center at St. Antony’s College, Oxford. "They are very concerned about having an Islamic alternative that is trying to trump the Saudi claim to being ruled by the Quran. To have someone declaring themselves a caliph is a direct challenge to the legitimacy of the Saudi monarchy."

Riyadh only recently repaired a serious rift with Qatar over its support for Muslim Brotherhood groups in the Arab world.

Iran, the bastion of Shiite Islam, represents another alternative version of the faith, but that rivalry has been around for 1,000 years. As Iranian political and military influence has grown in Iraq, Syria, Lebanon, Bahrain and now Yemen, however, Riyadh has felt it needed to act.

Lacking the military means to sway events in Syria, although Riyadh did support and fund anti-Assad rebels, Saudi Arabia instead turned to the oil weapon in order to try to influence Syria’s two main backers, Iran and Russia, some analysts said.

As worldwide demand softened, Saudi Arabia continued pumping, even as prices tumbled to around $50 from more than $100.

To maintain its own social spending, including $130 billion in benefits pledged to help ward off an uprising at home, the kingdom needs an oil price of $100 per barrel. But given its foreign reserves of around $730 billion, analysts said it could hold out for a few years with lower prices. Moscow and Tehran, both stalwart backers of Syria, are already suffering.

Riyadh is hoping to reach some deal with Iran on its influence in Iraq and Syria, as well as Moscow on the latter. In the past, such attempts resulted only in deals on oil, analysts said. On the oil front, the main goal of Saudi Arabia is to maintain its global market share and to undermine the development of alternative sources and technology, they said.

"Saudi oil policy will continue as it is regardless of the leadership,’" said John Sfakianakis, the Riyadh-based Middle East director for the Ashmore Group, an investment fund. "They can endure this for quite some time."

At home, the Saud family has maintained social peace through a combination of draconian punishments for those challenging its conservative doctrines and lavish spending on social benefits.

But the current situation in the region, analysts suggested, is the worst constellation of political and economic turmoil facing any monarch in 50 years. When King Faisal seized the throne in 1964 by deposing his own brother, the treasury was bare and across the region Arab nationalist adherents of the Egyptian leader, Gamal Abdel Nasser, including some in the Saudi military, sought the death of kings.

"Salman has plenty of challenges, but what he has at home is a relatively stable domestic political situation," said F. Gregory Gause III, the head of the international affairs department and a Saudi specialist at Texas A&M University.

Riyadh will remain a strong supporter of President Abdel-Fattah el-Sissi, who has restored military rule in Sunni Egypt.

"They like him because they like the Egyptian military, they see it as a stabilizing force," said Khalid al-Dakhil, a political-science professor and political analyst in Riyadh. "The Saudis and the Egyptian military are against the idea of revolution to start with, especially popular revolution."

Saudi Arabia has not been drawn directly into the Arab uprisings in Tunisia, which is relatively stable, nor Libya, although that may yet occur. Its main problem is right next door in Yemen.

Militiamen from the Houthis, a Zaydi sect of Shiite Islam but also traditional rulers of Yemen, are on the verge of seizing power. Given that the current fighters are backed by Iran and modeled themselves on Hezbollah in Lebanon, Saudi Arabia cut off the $4 billion it had been providing annually to the pro-American government.

But al-Qaida militants control large chunks of the south, where Sunni Muslims predominate. So the Saudis will ultimately have to choose a new ally where all are flawed.

"There is no political force in Yemen that can stabilize the situation there," al-Dakhil said.

The Saudis have long relied on the United States as their military umbrella, although that relationship soured after King Abdullah felt that President Barack Obama was ignoring the region, or at least Saudi concerns. According to a leaked diplomatic memo, in 2008 King Abdullah urged the United States to weigh military action against Iran to "cut off the head of the snake."

The Saudis are concerned about Washington coming to terms with Iran, and Riyadh, like Israel, relishes the split between Congress and the White House over more sanctions. And overall, their interests tend to diverge, especially when it comes to fighting al-Qaida and other extremist organizations, which receive some of their funding from Saudi sources.

"I think the Saudis and the Americans have developed the habit of coexisting with their disagreements," al-Dakhil said.

That too, was an attitude that emerged under King Abdullah and will likely endure.

"The default setting for the Saudis is always the status quo," Rogan said.

Neil MacFarquhar, New York Times

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