Still, even for the young Salman, the future was cloudy—due, in no small part, to the uncertain line of royal succession in the House of Saud. Since 1953, the kingdom of Saudi Arabia, one of the world’s last surviving absolute monarchies, has been ruled by six brothers, all sons of King Abdul-Aziz al Saud. Abdul-Aziz is the central figure in modern Saudi Arabia, having united the kingdom in 1932, after a series of wars. In the forties, he opened the country to large-scale oil production by Western companies and, after meeting President Franklin Roosevelt on an American destroyer in the Red Sea, struck an alliance with the United States, which has endured ever since. The Saudis guarantee access to oil; the U.S., in return, guarantees Saudi Arabia security from foreign enemies.

Abdul-Aziz was a prolific father—he bragged of having “married no fewer than a hundred and thirty-five virgins,” and he sired at least forty-two sons and fifty-five daughters. Since his death, in 1953, royal succession has been determined on the principle of agnatic seniority, whereby a king’s younger brother is preferred over his sons. In 2015, when his successor King Abdullah died, his brother Salman ascended to the throne; another, younger brother, named Muqrin, became crown prince. Muqrin, the son of a Yemeni concubine, was Abdul-Aziz’s last surviving son.

As the generation of Abdul-Aziz’s sons neared its end, tensions arose over who would be the first member of the next generation to become king. Saudi kings, though absolute in their authority, have traditionally ruled by consensus among the brothers; their sons, in turn, are placed in key positions across the government. Any one of Abdul-Aziz’s hundreds of grandsons could feel entitled to the throne.

Salman, during forty-eight years as governor of Riyadh, had earned a reputation as a ruthlessly efficient executive. “He was the family enforcer—he kept people in line, and he had a file on everyone,” Rashid Khalidi, a professor of history at Columbia, told me. Less than a year after becoming king, he removed his brother as crown prince and sent him into retirement; he elevated his nephew Mohammed bin Nayef to succeed him, and made his own son, Mohammed bin Salman, deputy crown prince.

Displacing a crown prince was an unprecedented move, but in many respects bin Nayef was a solid choice for a successor. For years, he had served as interior minister. After the attacks of September 11, 2001, he had presided over a vicious fight with Al Qaeda, in which his security forces tortured and killed suspected insurgents. In 2009, the group retaliated by sending a suicide bomber to kill bin Nayef, who suffered damage to one hand and lasting pain from his injuries. Bin Nayef forged close relationships with American officials. “He was the go-to person on counterterrorism,” a senior counterterrorism official in the Obama Administration told me. For King Salman, the choice of bin Nayef was politically astute for another reason: his only children were two daughters, which meant that his ascension would be less threatening to others, because no one in his bloodline could succeed him.

The selection of M.B.S. as deputy crown prince promised less stability. At twenty-nine years old, he was younger than many of his rivals but undeniably King Salman’s favorite. Joseph Westphal, the U.S. Ambassador to Saudi Arabia from 2013 to 2017, told me that whenever Salman introduced M.B.S. to a stranger he said, with evident pride, “This is my son.” Westphal recalled watching a video recorded when M.B.S. was a teen-ager, in which Salman visited an industrial plant with two of his sons, Faisal and M.B.S. Faisal, who is fifteen years older, walked passively, while M.B.S. asked questions and scribbled notes incessantly; Salman watched him and beamed. “He was in key meetings all the time—never interfering, just taking notes, but always switched on,” Westphal said of M.B.S. “I saw right away that this guy was going to be more than just a silent adviser to the King.”

M.B.S. gives the impression of being comfortable with Western mores. In meetings with American women, he shakes their hands and looks them in the eye, which not every Saudi official will do. Once, during a meeting at the home of Secretary of State John Kerry, M.B.S. spotted a grand piano, walked over, and began playing the “Moonlight” Sonata. His favorite diversion is Call of Duty, the video game. But his English is halting, and among his brothers—he has nine—he is unusually bound to Saudi Arabia. “M.B.S. is unlike his brothers, several of whom were educated in the West and one of whom has a doctorate from Oxford,” a longtime friend of M.B.S. told me. “If you look at them and you talk to them, they are basically soft. And there is this quality to M.B.S.—the guy’s not soft. He has a lot of charisma. He’s a lot like Bill Clinton. He makes you feel like you’re super important when you’re talking to him. He really puts on a charm that is unmistakable.”

As M.B.S. grew into adulthood, he brazenly used his status to enrich himself. In his teens, according to people who know him, he visited a series of wealthy businessmen and asked them to put money into his personal investment fund. In a matter of weeks, he raised thirty million dollars. “He’s the son of Salman,” M.B.S.’s friend told me. “It’s not like anyone was going to say no.” According to a story that circulates in Riyadh, M.B.S. demanded that a Saudi land-registry official help him appropriate a property. After the official refused, he received an envelope with a single bullet inside. The episode earned M.B.S. the street name Abu Rasasa, or “father of the bullet.” “The story is true,” the friend said. “I think that M.B.S. realizes that he went too far toward some people in those days, and he has tried to make amends.” (A spokesman for the Saudi Embassy denied the story, but largely declined to coöperate with fact-checking for the rest of the article, describing it as full of “old, incorrect rumors.”)

In addition to being deputy crown prince, M.B.S. was appointed to positions that gave him vast powers over foreign and domestic policy. He was named defense minister, head of the kingdom’s economic-planning council, and chief of Aramco, the national oil company and the central pillar of the country’s economy. In the seventy years since Saudi Arabia began exporting oil at scale, it has grown into the largest economy in the Middle East, with a welfare state whose benefits include free education and health care, along with subsidized food, electricity, and housing. But the economy relies overwhelmingly on oil; the country exports almost nothing else, and imports almost everything else, from food to freshwater. The welfare state was built on the expectation that the price of oil would remain at historic levels of at least a hundred dollars a barrel. It is now about sixty-two dollars, and is widely predicted to keep falling. “If you are the guy driving the Saudi bus, my advice would be to get off it as soon as you can,” Jan Stuart, an energy economist in New York, told me. The former defense official put it even more starkly: “In five to seven years, at current trends, they’re broke.”

The economic pressures on the Saudi state are likely to get worse. Close to seventy per cent of the population is under thirty years old. Every year, the government pays for as many as seventy thousand young people to study in the United States. Those students return home wanting jobs and, often, at least some of the freedoms that they enjoyed in the West.

To address these concerns, M.B.S. devised a plan, called Vision 2030, for a vast transformation of the Saudi economy and society. Working with consultants from McKinsey & Co., he set quantifiable goals to be met in the next decade. The new order would encourage entrepreneurship and foreign investment, and privatize state-owned industries, including the oil business. The workforce would be augmented by a growing number of women, along with nonprofit organizations and civic-minded volunteers. To publicize the plan, M.B.S. travelled to China, to Russia, and to the U.S., where he met with an array of tech executives, including Mark Zuckerberg. At a gathering of prominent venture capitalists at the Fairmont Hotel, in San Francisco, M.B.S. spoke bluntly about Saudi Arabia’s prospects. According to one attendee, he said, “In twenty years, oil goes to zero, and then renewables take over. I have twenty years to reorient my country and launch it into the future.”

The attendee said, “My jaw was on the floor. The meeting had the dynamic of a tech startup. He’s throwing the harpoon.”

M.B.S.’s appointments also allowed him to display his apparently irrepressible ambition. In April, 2016, when President Obama paid his final visit to Saudi Arabia, he and King Salman sat facing each other, with their aides grouped around them. Obama’s advisers noticed that, each time the President spoke, Salman, who was eighty, paused before answering, while M.B.S., several seats to his left, typed on an iPad. When M.B.S. finished, the King read from an iPad of his own and then responded to Obama. “The chances of that being a coincidence are quite low,” a former national-security official told me.

At another meeting, Obama upbraided King Salman for arresting dissident bloggers and for executing Shiite protesters, complaining that these practices made it difficult for him to defend the Saudis in the United States. According to several former American officials, M.B.S. rose abruptly from his chair to convey his displeasure to Obama. “Suddenly, he was standing up and saying, ‘You don’t understand our judicial system—we can get you a briefing,’ ” the former national-security official said. “It was very strange.”

When King Salman named bin Nayef crown prince, some Saudis speculated that the King envisioned him as a sort of caretaker, running the government until M.B.S. could be installed. “I don’t think Salman ever intended to make bin Nayef king,” a prominent Saudi analyst told me. “I think he was just waiting for the moment when M.B.S. was ready.” But bin Nayef was a popular figure, and bypassing him would have aroused resistance within the royal family. Outwardly, M.B.S. and bin Nayef worked smoothly together. M.B.S. adhered carefully to royal protocol; at meetings with foreign leaders, he sometimes asked bin Nayef’s permission to speak. In 2016, Joseph Westphal asked M.B.S. who he thought would succeed King Salman. “He said, ‘We have a crown prince, and historically the crown prince always becomes the king,’ ” Westphal told me.

Under the surface, though, tensions grew, as M.B.S. maneuvered to reduce his rival’s power. His directorship of the economy and of the military allowed him to crowd out bin Nayef’s daily duties. In the name of streamlining the government, he eliminated a council of advisers who answered to bin Nayef, depriving him of most of his professional staff. A former American official who maintains contacts in the region told me, “M.B.S. was literally signing orders in the King’s name.”

Saudi Arabia sees itself as the center of the Islamic world: the king is customarily known as the “custodian of the two holy mosques,” the sacred sites in Mecca and Medina. But, as M.B.S. gained power, he was aided by an ally from outside the kingdom: Mohammed bin Zayed, of the United Arab Emirates. Bin Zayed, or M.B.Z., is the crown prince of Abu Dhabi, the most politically important of the country’s seven emirates. Flush with revenue from oil and from the booming city-state of Dubai, M.B.Z., the country’s de-facto leader, has helped build the Emirates into a kind of Middle Eastern Singapore: rich, efficient, and authoritarian.

M.B.Z., fifty-seven, is a former military helicopter pilot, with a modest bearing that belies his influence throughout the Middle East. “If you sit down to talk to M.B.Z., he’s going to whisper, and he’s going to be very respectful and very polite,” Richard Clarke, a counterterrorism adviser to Presidents Obama and George W. Bush, told me. “You really have to get into his confidence over many years before he will raise his voice. And then he’ll argue with you.” He is unabashedly pro-American in a region teeming with anti-American sentiment; he has purchased billions of dollars’ worth of American weapons and has often been called on to advance U.S. prerogatives. In 2003, the U.A.E. volunteered to send a small contingent of troops to assist in Afghanistan, the first Arab country to do so; fifteen years later, they are still there.

Saudi Arabia and the U.A.E., which share a border, are both hereditary monarchies, dominated by Sunnis, and their interests often align. In foreign affairs, Saudis prefer to see the U.A.E. as their junior partner, but, in many respects, it is M.B.Z. who drives the policy. From early on, he opposed bin Nayef’s rise, in part because of an unresolvable dispute between the two men. In a 2003 U.S. diplomatic cable, published by WikiLeaks, M.B.Z. was quoted comparing bin Nayef’s father to an ape, suggesting that he provided evidence that “Darwin was right.” The former American official with contacts in the region told me, “After that, there was no possibility of a relationship between M.B.Z. and bin Nayef.”

More important, M.B.Z. saw M.B.S. as a younger version of himself: smart, energetic, and eager to confront enemies. As M.B.S. was being groomed for power, the Gulf states were feeling increasingly vulnerable. When the Arab Spring erupted, in 2011, it forced out dictators in Tunisia, Egypt, and elsewhere. Leaders in Saudi Arabia and the Emirates were terrified that their monarchies would soon follow. The emergence of isis further alarmed them, and the two countries supported proxies to fight against its incursions in Syria and in Libya. But their most decisive intervention came in Egypt, the Arab world’s most populous country, where the longtime strongman Hosni Mubarak was ousted by a popular uprising. In June, 2012, Egyptian voters delivered the Presidency to Mohamed Morsi, of the Muslim Brotherhood. For the Saudis and the Emiratis, it was a nightmare.

The Brotherhood, founded in 1928, is the world’s largest Islamist movement, with hundreds of millions of followers. It has inspired Islamist political parties throughout the Sunni Muslim world, including branches in Jordan, Syria, and Bahrain. In Egypt, security services had savagely repressed the Brotherhood for decades. After the Arab Spring, though, it emerged as the country’s most organized political force.

“When Morsi got elected, the Saudis and the Emiratis went into overdrive,” a former senior American diplomat told me. According to several former American officials, M.B.Z. and Bandar bin Sultan, the director of Saudi intelligence, began plotting with others in their governments to remove Morsi from power. Egypt’s generals were already organizing against him. Bandar and M.B.Z. reached out to the Egyptian defense minister, General Abdel Fattah El-Sisi, and promised twenty billion dollars in economic aid if Morsi were deposed. (The Emirati Embassy did not respond to requests for comment.) They also began financing an anti-government movement in Cairo, built around an ostensibly independent youth group called Tamarod. As the coup took shape, Bandar and Sisi used Mohammed Dahlan, a Palestinian confidant, to carry messages and money to collaborators in the Egyptian military. The former diplomat said that the foreign support was crucial to the coup: “For Sisi to move like that, he needed a promise that he would succeed.” In July, 2013, the Egyptian military forced Morsi from power, and soon afterward it orchestrated a crackdown on suspected Brotherhood supporters, detaining at least forty thousand people. “It was terrible, terrible,” the diplomat told me. “What the Saudis and the Emiratis did was unforgivable.”

As M.B.S. gained influence in the kingdom, he and M.B.Z. built a close relationship. “They talk on the phone all day to each other,” Clarke told me. The two royals share a view of geopolitics. M.B.S. has referred to the Muslim Brotherhood and its allies as “forces of evil,” and, like M.B.Z., he considers Iran his country’s great enemy. The rivalry dates to the time of the Safavid Empire, which swept out of Persia in the fifteen-hundreds and ruled parts of the Arab world for two centuries. In recent years, Saudi and Emirati officials have watched in alarm as the Shiite regime in Iran has established an increasingly dominant presence throughout the region. “The Nazis and the Iranian regime are ideologically very similar,” Thamer al-Sabhan, the Saudi minister for Gulf affairs, told me. The Iranians were assembling “a new Islamic army that relies on chaos and aggression,” he said. “They don’t want to weaken Saudi Arabia—they want to take over the region altogether. Their only speed bump is the kingdom.”

In 2009, the Obama White House began negotiating with the Iranians to limit their nuclear program. Saudi and Emirati leaders viewed any outreach to Iran as dangerously misguided. An American national-security official recalled visiting the Emirates in 2011 to meet M.B.Z. He told me that he was instructed to wait on a dock on the Persian Gulf; eventually, M.B.Z. pulled up in a speedboat, wearing shorts, flip-flops, and a Bass Pro Shop hat. “He read us the riot act,” the official recalled. “He told us that we were naïve about the Iranians, and that we were giving away the whole region to them. That was always what the Emiratis and the Saudis said—we were naïve. We thought they were reckless.”

After M.B.S. was named defense minister, the tension with the Obama Administration intensified, particularly over another conflict with Iran—this one in Yemen, which borders Saudi Arabia to the south. Yemen is a poor country, perpetually beset by internal violence. For three decades, Saudi Arabia had spent millions of dollars a year subsidizing tribal leaders there, in order to buy a little peace. In recent years, the country had fallen into civil war, and, after a ceasefire brokered by the Saudis fell apart, a Shiite-dominated rebel group known as the Houthis had swept into the capital and forced the President to flee. Saudi leaders were deeply suspicious of the Houthis, whom the Iranians periodically supplied with weapons.

In March, 2015, the Saudis and the Emiratis informed the White House that they were preparing a military intervention in Yemen. “M.B.S. told us he wanted us with them, but that they were going anyway,” a former State Department official told me. For years, the Obama Administration had been telling the Saudis that they had to carry more weight in the region; now, it seemed, M.B.S. was calling their bluff.

The Administration declined to directly join the campaign, but, soon after the war began, Tony Blinken, the Deputy Secretary of State, flew to Riyadh to meet with M.B.S. “He told me his goal was to eradicate all Iranian influence in Yemen,” Blinken said. He was taken aback; to purge Iran’s sympathizers from the country would require a bloodbath. “I told him, You could do many things to minimize or reduce Iranian influence. But eliminate it?” After M.B.S. sent Saudi forces into Yemen, the Emiratis circulated celebratory photomontages online, in which M.B.S. looked on sternly as lions and fighter jets menaced his foes.

As the war increased M.B.S.’s influence in Saudi Arabia, he began pushing more aggressively to become crown prince. In the summer of 2015, Adel al-Jubeir, the Saudi foreign minister, was dispatched to Nantucket to see Secretary of State Kerry, who was vacationing at his house there. Jubeir wanted to know whether Kerry would support M.B.S. if he pushed bin Nayef aside, according to a former Obama Administration official who was briefed on the meeting. “M.B.S. was trying to play Kerry,” the official told me. “He wanted us on his side.” Kerry said that the Administration wasn’t going to take sides. At about the same time, the official told me, bin Nayef was reaching out to John Brennan, who was then the head of the C.I.A., to seek support against M.B.S.

Inside the Obama White House, fears grew that the struggle for succession would turn violent. As defense minister, M.B.S. controlled the Army; as interior minister, bin Nayef controlled the country’s vast internal security forces. “You had the possibility of the princes going to war with each other, with tanks in the streets,” the former official said.

In Washington, M.B.Z. undertook a campaign to help establish M.B.S. as the next Saudi king. “The Saudis and the Emiratis have the most effective lobbying operation in Washington,” Ben Rhodes, Obama’s deputy national-security adviser, told me. “I would say they are more responsible for the image of Obama as being soft in the Middle East than anyone else. They trashed us all around town.” Rhodes described Yousef Al Otaiba, the U.A.E.’s Ambassador to the United States, as especially capable. Otaiba, an urbane man with a shaved head and a wardrobe of immaculately tailored suits, meets often with America’s financial and political élites, sometimes arriving by private jet. Otaiba extolled M.B.S. to a range of powerful ex-officials, including David Petraeus, the former general who is now at the investment firm Kohlberg Kravis Roberts, and Tom Donilon, who served as President Obama’s national-security adviser. In discussions with members of the Obama Administration, he described his client in prophetic terms. “M.B.S. is going to be king for fifty years,” a former senior White House official recalled him saying.

Otaiba also appears to have helped organize a series of op-eds promoting M.B.S., in which he demonstrated unusual influence over prominent Washington figures. “I know you have a P.R. firm,” Frances Townsend, former President George W. Bush’s counterterrorism adviser, wrote to Otaiba, as she proposed an article favorable to M.B.S. “Let me know if there is someone I should work with that might provide a draft for me to begin from.” The former American official with contacts in the region said that Otaiba’s work was part of a larger effort, in which the Emiratis hired other lobbyists on M.B.S.’s behalf. (Otaiba denied this.) “All these public-relations firms that were promoting M.B.S. in the United States were paid for by Abu Dhabi,” the official said.

Bin Nayef, alarmed by what he saw as foreign interference, wrote to King Salman to warn him. (The letter was given to me by the former American official.) “We are facing a dangerous conspiracy,” he wrote. “An Emirati plot has been exposed to help aggravate the differences within the royal court.” He added, “Bin Zayed is currently planning to use his strong relationship with the United States President to achieve his intentions.”

In December, 2016, M.B.Z. flew to New York to meet with President-elect Trump, Kushner, Bannon, and Michael T. Flynn, who had been appointed national-security adviser. It’s customary for foreign leaders to notify the American government when they travel to the U.S., but M.B.Z. did not do so. The meeting has since reportedly captured the interest of Robert Mueller, the special counsel investigating Russia’s interference in the 2016 election, who is looking into allegations that Emirati lobbyists funnelled millions of dollars to Trump-campaign donors.

M.B.Z. arrived at the meeting, in the Trump Tower penthouse, with an entourage of about thirty people. He was dressed in combat boots and jeans, and some of his men were armed. For most of the first hour, he and the Trump aides engaged in a relatively conventional discussion of Middle East policy, but the talk grew more animated as the two sides realized that they shared a common fixation on Iran. The meeting evolved into a planning session on how the Trump White House would confront the Iranian regime in the Gulf.

A few weeks later, just after the Inauguration, Kushner began advocating a new outreach to Saudi Arabia. In his plan, Trump would visit Riyadh for a summit of fifty-five Muslim-majority countries. “Jared was the engine for all this,” the former defense official said. In a single gathering, Trump could introduce himself to the Muslim world, reëstablish America’s relationship with Saudi Arabia, put Iran on notice, and communicate to everyone present how the Administration felt about M.B.S. “The whole establishment was opposed to it—State, D.O.D., Treasury, everyone,” the former defense official said. There were concerns about endorsing M.B.S. and rupturing the relationship with bin Nayef. “The fear was: You can’t engage with M.B.S. You can’t be doing this stuff, because that’s going to upset things. It might show favoritism. We’ve got a partner. Let’s stick with stability.”

At a meeting, aides raised reservations about the summit. “We go around the room like this for an hour or so,” the official said. “And Jared stood up and said, ‘All right—I understand this is ambitious. But we won’t know if the Saudis will deliver unless we really test them.’ ”

The summit, in May, 2017, was Trump’s first overseas trip as President. The Saudis treated him as a fellow-monarch, spending an estimated sixty-eight million dollars on festivities, including a ceremony in which Trump and a group of royals danced, with swords in hand, to a traditional chant. In meetings, Bannon told me, Trump was blunt about American aims: “No. 1, Trump said to them, Stop funding Islamic terrorism. No more fucking games.” At the summit, the Saudis, the Qataris, and others promised to fight extremism, and the Saudis agreed to pay for a jointly run counterterrorism center. The United States announced that it would sell the Saudis some hundred and ten billion dollars’ worth of arms. A Pentagon official later said, “When completed, it will be the largest single arms deal in American history.” Like the pledge to fight terrorism, these agreements were nonbinding, but Bannon maintained that Trump had produced a decisive change in Saudi policy.

In the American press, the summit was noted largely for its pageantry, which culminated in the opening of the counterterrorism center, where Trump, King Salman, and Sisi posed in a huddle around a luminous globe. (The late-night host Stephen Colbert cracked, “Fellas, if I may, you need to work on your not-looking-like-supervillains skills.”) But, in the months that followed, a series of dramatic events suggested that the attendees had quietly made a number of major decisions. Trump declared that the U.S. would move its Embassy in Israel from Tel Aviv to Jerusalem, something that no American President had attempted since Israel occupied the West Bank, in 1967. M.B.S. leapfrogged over bin Nayef to become crown prince. And the Gulf monarchies, led by Saudi Arabia, entered an open confrontation with Qatar.

The first sign of conflict came on the evening of May 23rd, when a series of unusual quotations began to crawl across the bottom of television screens tuned to the official news agency of Qatar, a tiny, thumb-shaped emirate on the Persian Gulf. “Iran is an Islamic power in the region that cannot be ignored,” one said. “Hamas is the legitimate representative of the Palestinian people,” another said. The statements would have been unremarkable, except that they were attributed to Tamim bin Hamad al-Thani, the Emir of Qatar. For a royal in the Gulf, any open endorsement of Iran is explosive.

Thani claimed that the remarks were fakes, planted onscreen by hackers working for enemies of Qatar, but they prompted a stern reaction. Saudi Arabia’s most prominent news network aired coverage—widely understood to have been personally overseen by M.B.S.—that attacked the Qatari leadership. (“Doha has lost its mind,” a prominent intelligence official said.) In a statement on June 5th, the Saudi government accused Qatar of “dividing internal Saudi ranks, instigating against the state, infringing on its sovereignty, adopting various terrorist and sectarian groups aimed at destabilizing the region.” The same day, Saudi Arabia and the Emirates, along with Bahrain, announced that they were blockading Qatar and breaking off diplomatic relations. The moves were effectively acts of war.

The Gulf countries that joined the blockade had long accused Qatar of financing terrorism and revolution across the Middle East and of aligning itself too closely with Iran. In 2013, they were divided by the crisis in Egypt, with Qatar providing financial support for the Morsi government and the Saudis and the Emiratis backing the Army. Saudi and Emirati leaders complain about Qatar’s sponsorship of the Muslim Brotherhood and of Hamas, the Palestinian group that rules Gaza and whose roots are in the Brotherhood; they also resent the popularity of its state-funded television network, Al Jazeera, which is often sharply critical of the Gulf monarchies. M.B.S. has spoken dismissively of Qatar as a nagging problem that can, with sufficient resolve, easily be fixed. “Qatari behavior toward the Arab countries is motivated by psychological problems,” he said. “One Saudi minister could solve the whole Qatari crisis.”

The U.S. government has a complex relationship with Qatar, which has often been willing to facilitate difficult diplomatic maneuvers. Although the United States lists Hamas as a terrorist organization, a former American diplomat told me that after the group’s leader, Khaled Meshal, was forced to flee the Assad regime, in 2012, American diplomats asked the Qataris to take him in. Since then, he has lived in a compound around the corner from the U.S. Ambassador’s residence. The Qataris also host a de-facto embassy for the Taliban, where U.S. diplomats can speak with Taliban officials; Bo Bergdahl, an American soldier who had been captured by the Taliban in Afghanistan, was released through negotiations conducted there. Perhaps most important, Qatar is the site of Al Udeid Air Base, the U.S. military’s principal forward base in the region, which houses some eleven thousand military personnel and hundreds of combat aircraft. The Qataris funded its construction and continue to pay most of its operating costs. “All of these things, we have done at the request of the Americans or in coördination with them,” Qatar’s foreign minister, Mohammed bin Abdulrahman, told me.

Nevertheless, after the blockade began, President Trump tweeted his support, writing, “During my recent trip to the Middle East I stated that there can no longer be funding of Radical Ideology. Leaders pointed to Qatar—look!” (The former American diplomat suggested that his enthusiasm was partly motivated by ignorance: “I am convinced that Trump didn’t know that we had a military base in Qatar. He had no idea.”) Other senior officials expressed horror. Secretary of State Rex Tillerson and Secretary of Defense James Mattis were on a trip to Australia when the crisis broke, and were taken by surprise. “Tillerson was very upset,” a senior State Department official told me. “He couldn’t believe that the Saudis and the others would try something like that.” Tillerson began working to ease tensions. Mattis called the Saudis and urged them to stand down. “Mattis told M.B.S., ‘It’s not the time for a war,’ ” a former senior Pentagon official told me. “The phone call didn’t go very well.” American officials became so worried about the possibility of a military clash that they sent a drone to monitor the border.

In the days that followed, the Saudis and their allies imposed conditions that appeared designed to reduce Qatar to a vassal state; in order for the blockade to be lifted, the country would, among other things, have to close Al Jazeera and sever relations with Iran. American officials concluded that M.B.S. and M.B.Z. were preparing to overthrow Qatar’s government. “They have made it clear, privately and publicly, that their intention was to replace the Emir,” the former American diplomat told me. “I think they were going to invade.” Qatar presented an almost irresistible target: though its population is barely three hundred thousand, it controls one of the world’s largest natural-gas fields and has a sovereign wealth fund worth an estimated three hundred billion dollars. “If you look at it from a financial perspective, invading Qatar makes a lot of sense,” the diplomat said. The government of Turkey, which had a military base in the capital, sent a new detachment of soldiers.

Behind the scenes, there were indications that the plan had been approved at the summit in Riyadh. As the blockade was getting under way, a senior American official received a telephone call just before midnight from Yousef Al Otaiba, the Emirati Ambassador, who told him what was happening. “I was very angry,” the official told me. “I tried to talk him out of it.” When the official complained that the State Department had been given no notice, Otaiba suggested that he’d already announced it to the Administration. “I’ve informed the White House,” he said. A former American intelligence official told me it was inconceivable that the Saudis or the Emiratis would have acted without approval from the U.S. “I think it’s pretty well understood that the White House gave the green light,” the official told me. (A senior Administration official denied this.)

American diplomats knew almost nothing about what was happening between the White House and the Gulf monarchies. More than a year into Trump’s term, he still has not named an Ambassador to Saudi Arabia. “Nobody knows what happened in Riyadh, because there were no diplomats in the room,” the former American diplomat told me. At a speech several months after the crisis in Qatar erupted, Bannon told an American audience, “I don’t think it was just by happenstance that, two weeks after that summit, we saw the blockade.”

Some Qataris speculate that Kushner endorsed the blockade partly out of frustration over a failed deal with his family’s real-estate firm. In April, a month before the summit, Qatar’s finance minister, Ali Sharif al-Emadi, flew to New York to examine new investment opportunities. He and his entourage rented a suite at the St. Regis Hotel, cleared away most of the furniture, and received a long line of American businessmen who were looking for funding. According to a financial analyst with knowledge of the meeting, among the hopefuls were Kushner’s father, Charles, and his sister Nicole. They came seeking money to rescue the family’s signature property, 666 Fifth Avenue—a forty-one-story tower in midtown Manhattan, which generates gallingly low returns and carries a mortgage, due next February, of $1.2 billion.

Charles Kushner has maintained that the Qataris requested the meeting, and that he attended out of politeness but was too wary of conflicts of interest to accept funding. The financial analyst, however, said that Kushner pitched a huge renovation of the property, which included bringing in retail stores and converting offices to residences, and hosted a follow-up meeting the next day at 666 Fifth Avenue. “He asked for just under a billion dollars,” he told me. The Qataris declined, citing dubious business logic. “They could have bought the building—believe me, they have the money,” the analyst said. “They just didn’t think it would ever pay off.” The analyst worried that refusing the deal had a political cost. “Here’s a question for you: If they had given Kushner the money, would there have been a blockade? I don’t think so.”

As the conflict wore on, op-ed writers and social-media posts kept up a drumbeat against Qatar. Many of them came from a curious source: the SCL Group, the parent company of the political-research firm Cambridge Analytica. (Before the election, Bannon was a vice-president of Cambridge Analytica, which was financed by Robert Mercer, the billionaire investor and Trump supporter.) SCL had been retained by the Emirati government; this was not known at the time, because the firm did not declare to the U.S. government that it was working for the U.A.E. until the following month.

Eventually, U.S. intelligence analysts determined that the Qataris had been telling the truth: the televised statements attributed to Emir Thani had been fabricated by hackers hired by the United Arab Emirates. “The hacking was a pretext for us to be attacked,” bin Abdulrahman, the Qatari foreign minister, told me. Other indications emerged that the crisis had been premeditated. Last summer, Otaiba’s e-mails were hacked. Financial documents found among them showed that Emirati officials had, through a bank in Luxembourg, plotted a campaign of financial warfare aimed at causing Qatar’s currency to crash.

Qatar remains under blockade by the allied countries in the Gulf. The blockade has inflicted deep losses on the economy and forced leaders to find alternative sources of food and consumer goods. But the Qataris are rich enough to endure without too much hardship, and they have emerged from the crisis as objects of sympathy. In June, Mattis approved a deal to sell Qatar twelve billion dollars’ worth of American-made F-15 fighter jets. At a subsequent gathering, Tillerson reassured regional officials that Qatar was a “strong partner and longtime friend of the United States.”

On the evening of June 21st, viewers of Al Arabiya, the Saudi state news channel, witnessed a surreal scene: M.B.S., his face shrouded by a red-and-white checked kaffiyeh, strode up to his rival bin Nayef, theatrically kissed his hand, and dropped to his knees. Before M.B.S. could explain himself, bin Nayef declared his fidelity to his cousin: “I pledge allegiance to you, through the best and the worst.” M.B.S. stood up and, furiously shaking bin Nayef’s hand, offered his own affirmation: “We will always seek your guidance.” The film clip, twenty-four seconds long, was intended to announce that M.B.S. had peacefully succeeded bin Nayef as the next king of Saudi Arabia.

In fact, the transfer of power was anything but amicable. The night before, according to Saudi and American sources, bin Nayef had been summoned to a meeting with King Salman. At the palace, guards surrounded him, confiscated his phone, and demanded that he abdicate. Bin Nayef refused. According to the former American official with contacts in the region, he was forced to stand for several hours, which, because of lingering injuries from the suicide attack, caused excruciating pain. One source told me that the guards threatened to announce that bin Nayef was addicted to painkillers, an allegation that the former American official dismissed: “I really doubt he did anything like that.”

As dawn neared, bin Nayef agreed to surrender his position. M.B.S. installed a new interior minister, a relative believed to be loyal to him. Bin Nayef was confined to his house, where even some of his most powerful American friends, including the former C.I.A. directors George Tenet and John Brennan, were not able to reach him. M.B.S.’s way to the throne was finally clear.

In the months that followed, M.B.S. pushed a sweeping reform agenda, decreeing, among other things, that women be allowed to drive. The Saudi state has long ruled through an alliance with the standard-bearers of the Wahhabi creed, who, in exchange for their loyalty, were given permission to disseminate stringent and antiquated doctrines. M.B.S. drastically scaled back funding for the spread of Wahhabism abroad, which many experts believe to be responsible for encouraging terrorism and virulently anti-Western ideas. “All we are doing is going back to what we were—moderate Islam that is open to all religions and open to the world,” M.B.S. told a gathering at the Ritz-Carlton in Riyadh, in October. “We will not waste thirty years of our lives in dealing with extremist ideas. We will destroy them today.”

These moves drew widespread, if not unanimous, praise in the West. Thomas Friedman, the influential foreign-affairs columnist for the Times, describedvisiting M.B.S. and returning convinced that his reforms, if they succeed, “will not only change the character of Saudi Arabia but the tone and tenor of Islam across the globe.” Friedman wrote that the young crown prince had kept him up until one-thirty in the morning, discussing national renewal until he pleaded exhaustion. “It has been a long time,” he wrote, “since any Arab leader wore me out with a fire hose of new ideas for transforming his country.” The column inspired outrage among critics of Saudi Arabia. The Al Jazeera journalist Mehdi Hasan called it “an embarrassment.” At a Brookings Institution event a few days later, Friedman responded brusquely. “I got news for you—the entire Arab world is dysfunctional right now,” he said. “And so when I see someone who is having the balls to take on the religious component of that, to take on the economic component, to take on the political, with all of his flaws . . . I wanna stick my head up and say, ‘God, I hope you succeed.’ And when you do that the holy hell comes down on you. Well, ‘Fuck that’ is my view, O.K.?”

As M.B.S. was being debated in the Western media, he began to systematically eliminate any potential opponents of his rule. In the next several months, Saudi police enforced a crackdown on what remained of the country’s independent press and pro-reform groups, arresting human-rights activists, pro-democracy organizers, and prominent journalists. “Most of the clerics he is arresting are not the hard-line clerics but the reformers—because they are popular,” Jamal Khashoggi, a Saudi journalist who recently fled to the U.S., told me.

Soon after becoming crown prince, M.B.S. had asked Western and Saudi banks to help assemble a financial picture of the country’s wealthiest men. On November 4th, he sent police across the country to arrest scores of people, including more than a dozen members of the royal family, on allegations of corruption. It was a breathtaking assault on the most powerful class of Saudis, who had enriched themselves, often with bribes and kickbacks facilitated by links to the royal family. M.B.S. warned, “Anyone who is involved in corruption will not be spared, whether he is a prince, a minister, or whoever he is. If there is enough evidence against him, he will be held accountable.”

Some two hundred detainees were brought to the Ritz-Carlton in Riyadh—a domain for princes, but not usually for princes under arrest. Among them were the country’s leading plutocrats, including a dozen senior princes, the owner of one of the country’s major television networks, the head of the national guard, and Al-Waleed bin Talal, a major shareholder in Citibank, 21st Century Fox, Apple, and Twitter, who has a net worth of seventeen billion dollars. Many were rattled by their first encounter with any restrictions on their lives. Ali Shihabi, who runs a pro-Saudi think tank in Washington, spoke to several detainees, and told me that everyone endured the same protocol: They were told to remove their clothes and were given a uniform and a medical exam, during which they were asked if they were taking any prescription drugs. Then they were led to guarded rooms, where the doors had been removed, along with the mirrors and anything else that they might use to harm themselves. “They could watch TV, order room service,” Shihabi told me. “They just couldn’t leave.”

Then the interrogations began, with police and investigators presenting the detained Saudis with purported evidence of their misdeeds. A figure was usually arrived at—under coercion—and, once the detainees paid up and signed a nondisclosure agreement, they were free to leave. “There was no due process of any sort, no courts, no judges, no warrants—none of that,” a Western diplomat told me. Many wealthy Saudis who were not targeted in the crackdown frantically moved their money out of the country, the beginning of a capital flight that totalled millions of dollars a month.

While M.B.S. was preaching austerity to his countrymen, he seemed unwilling to restrain himself. In 2015, while vacationing in the South of France, he had bought a yacht, the Serene, from a Russian vodka tycoon, for five hundred and fifty million dollars. He bought a château west of Paris, with a cinema and a moat with a submerged glass chamber for viewing carp. And, last November, he reportedly spent four hundred and fifty million on “Salvator Mundi,” the Leonardo da Vinci portrait of Jesus Christ. A spokesman for the royal family dismissed the reports, saying that a distant relative of M.B.S. had bought the painting; it was meant to hang in the newly opened Louvre Abu Dhabi, where the crown prince’s friend M.B.Z. had recently welcomed the first visitors.

In the Saudi and the Western media, M.B.S. described the arrests as a crackdown on corruption, which, he claims, has recovered more than a hundred billion dollars for the state. “He was sending a message that the old era was over, that corruption would no longer be tolerated,” Bernard Haykel, a professor of Near Eastern studies at Princeton who has often met with the crown prince, told me. M.B.S. seems happy to have amplified his message, even if it was through brutal interrogations. At least one prominent Saudi died, in unclear circumstances. According to a Saudi with knowledge of the events, Ali al-Qahtani, a retired Army general, died of a heart attack after being subjected to harsh treatment during interrogation in the Ritz. (The Saudi government has denied abuse.) A detainee also told the Saudi that Amr al-Dabbagh, a former senior official with the Saudi Investment Authority, was subjected to electric shocks at the hotel. Some of those who had been inside the Ritz-Carlton reported that the captors spoke English to one another, which raised the possibility that M.B.S. had recruited foreigners to help him.

Haykel defended the detentions, saying that without them Saudi Arabia would continue on its unsustainable path. “M.B.S. knows that the system is incapable of reforming itself,” he said. “Why? Because the system as it presently stands has lots of royals and hangers-on and businessmen who are feeding at the trough and will never agree to disenfranchise themselves.” Even so, it seems clear that M.B.S.’s campaign functioned at least as much as an attack on those who might constitute a threat to his rule. Many of those arrested were relatives of previous kings—young men who considered themselves possible heirs to the throne, or at least to some aspect of the kingdom’s power. The most telling arrest was that of Prince Miteb bin Abdullah, the head of the national guard and a son of the late King Abdullah. By removing Miteb, M.B.S. gained effective control over all three of the country’s security branches: the Army, the interior ministry, and the national guard. “He can do whatever he wants now,” Khashoggi, the Saudi journalist, said. “All the checks and balances are gone.”

In late October, Kushner paid an unpublicized visit to M.B.S., his third trip to the kingdom since the election. Though Kushner was supposed to focus on a plan for peace between Israel and Palestine, he had evidently decided that the more pressing goal was to unite the region against Iran.

Soon after Kushner departed, M.B.S. held a meeting with Mahmoud Abbas, the leader of the Palestinian Authority, to discuss the prospects for peace in the Middle East. According to a former Obama Administration official, the Saudis presented a plan that was radically favorable to Israel. It would recognize Israel’s claims to Jerusalem and ratify nearly all of its settlements in the West Bank, offering the Palestinians only limited autonomy in areas under their control. A senior Palestinian official told me that Arab leaders have been applying intense pressure to Abbas, apparently in coöperation with the Trump Administration: “The whole idea is to settle the Jerusalem issue, so the White House can build a united front against Iran.” But, he said, “if Jerusalem is on the table, we will never do it.”

Around the same time, M.B.S. summoned Saad Hariri, the Lebanese Prime Minister, to Riyadh. Hariri got the call as he was preparing for lunch with Françoise Nyssen, the French minister of culture, but he was not in a position to ignore M.B.S. Hariri was a Saudi citizen, and his construction company, Saudi Oger, which was deeply in debt, had done millions of dollars’ worth of projects for the Saudi state.

M.B.S.’s relationship with Hariri had deteriorated because of the ongoing proxy war with Iran. Since the Saudis and the Emiratis intervened in Yemen, nearly three years earlier, things had gone disastrously wrong. The Houthis still occupied the capital, and Iranian élite commandos and operatives from Hezbollah were training new rebel fighters. Even more pressing, the Iranians had smuggled in missiles, which the rebels were using to bombard Saudi Arabia. In an effort to stop the missiles, the Saudis and the Emiratis blockaded Yemeni ports, which intensified the humanitarian disaster. More than ten thousand people have died, and hundreds of thousands more are facing famine and outbreaks of cholera.

Adding to M.B.S.’s anxiety was Hezbollah’s position inside Lebanon. Since the Lebanese civil war ended, in 1990, Saudi Arabia had given the country billions of dollars to help it rebuild, only to watch as Hezbollah grew into the strongest party and the dominant military force. For several years, the American and the Saudi governments had teamed up to build a Lebanese Army as a counterweight. In 2016, a year after M.B.S. took over as defense minister, he cancelled three billion dollars of military aid, concluding that it was a waste of money. “He felt like every dollar he sent to Lebanon was supporting Hezbollah,” the former American official who sees M.B.S. periodically told me.

The Saudis hoped that Hariri would be able to confront Hezbollah. He was a Sunni, and an experienced politician, who had served as Prime Minister from 2009 to 2011, when he fled to Paris, largely out of fear that Hezbollah was preparing to kill him. (His fears were not unfounded. In 2005, his father, Rafik, another Saudi-backed Prime Minister, was killed in a car-bomb attack, for which a U.N. tribunal has indicted four members of Hezbollah.) In 2016, after two years of parliamentary deadlock, in which the country operated without a head of state, he returned and took office.

But Hariri was unable to thwart Hezbollah, even as M.B.S. pushed him to take a tougher stand. The breaking point came in early November. As the rebels continued to fire missiles across the border, Ali Velayati, a senior Iranian leader, flew to Lebanon and met with Hariri. According to the former American official, Velayati said that Iran intended to continue asserting itself in the region. Afterward, Hariri posed, smiling, for a picture with him. When word reached M.B.S., he was enraged. “He felt like he had to do something,” the official said.

When Hariri was summoned to meet M.B.S., he expected a warm reception from the royal family. “Saad was thinking that all his problems with M.B.S. would be solved,” an aide to Hariri told me. Instead, in Riyadh, he was confronted by police, who took him into custody. According to two former American officials active in the region, he was held for eleven hours. “The Saudis put him in a chair, and they slapped him repeatedly,” one of the officials told me. (Hariri’s spokesman denied this.) At the end, in a surreal video that was played on Saudi television, Hariri, looking exhausted and drawn, read a resignation speech, claiming that he had fled Lebanon to evade an Iranian plot to kill him. Hariri, who is usually soft-spoken, declared that “Iran’s hands in the region will be cut off”—a statement that convinced many Lebanese that the speech had been written by someone else.

It was unclear who would become Lebanon’s new Prime Minister; according to Lebanese and Western officials I spoke to, M.B.S. had tried to enlist Hariri’s brother, Bahaa, who spends much of his time in Monaco, to take the position. A senior American official in the Middle East told me that the plot was “the dumbest thing I’ve ever seen.” But there were indications that M.B.S. had coördinated his moves with the Trump Administration, possibly at the summit in Riyadh. A former senior intelligence official who is close to the White House told me that M.B.S. had received a “green light” to remove Hariri. (A senior Administration official denied this.) “It’s disruptive,” the intelligence official told me. “The status quo in the Middle East doesn’t work. They want to break it up.”

Western officials, caught off guard by Hariri’s detention, rallied to save him. Tillerson released a statement, saying, “The United States supports the stability of Lebanon and is opposed to any actions that could threaten that stability.” Emmanuel Macron, the French President, visited M.B.S. and pressed him to release Hariri. According to a Western diplomat with knowledge of the exchange, M.B.S. opened the conversation by threatening to cut off trade with France unless Macron stopped doing business with Iran. Macron gently replied that a country like France was free to trade with whomever it wished. “Macron handled it very well, and M.B.S. backed down,” the diplomat told me.

Ultimately, the plan collapsed when most of the Lebanese political establishment protested Hariri’s captivity. Two weeks after he had arrived, Hariri was on a plane, going first to meet with officials in Paris and Cairo, and then on to Beirut, where he basked in sympathy. “The whole country is unified around him,” a senior Hezbollah leader told me.

Several days after his return, I went to see Hariri in Beirut. He lives in the Beit al-Wasat neighborhood, inside a high-walled compound of exquisitely restored villas with views of the Mediterranean; a few doors down sits the Maghen Abraham synagogue, destroyed during the civil war and rebuilt with the help of Hariri’s family. Despite the grand surroundings, he seemed less a returning hero than an exhausted former prisoner. “I don’t want to talk about what just happened,” he said, slumped behind his desk. “M.B.S. was right, O.K.? What he is trying to do is right.”

In March, M.B.S. began a two-week tour of the U.S., in which he travelled to New York, Boston, Houston, and Los Angeles, seeking investments and attempting to build good will. News stories had begun to spread about M.B.S.’s relationship with the White House, including one in which he reportedly said that Jared Kushner was “in his pocket.” Still, at a meeting in the White House Cabinet Room, Trump and Kushner received him warmly. “Saudi Arabia is a very wealthy nation,” Trump said afterward, in the Rose Garden. “And they’re going to give the United States some of that wealth, hopefully, in the form of jobs, in the form of the purchase of the finest military equipment anywhere in the world.” That same day, the Senate blocked a resolution to limit U.S. involvement in the war in Yemen.

In Saudi Arabia, too, M.B.S. is encountering little resistance. “Working for M.B.S. is a blessing,” Mohammad al-Shaikh, the Saudi minister of state, told me. “He’s just gifted.” Shaikh spoke of ambitious ventures throughout the country: a hundred and ten miles of subway track being dug under Riyadh; a megacity, called Neom, to be constructed on the Red Sea coast. The cost would be tremendous, he acknowledged, but he said that it would be offset by efficiencies in government, achieved by a newly formed agency called the Bureau of Capital and Operational Spending Rationalization. He described the changes as a kind of enlightened revolution. “It’s a choice,” he said. “It’s not the Arab Spring. This is the leadership deciding that we have a huge potential we need to unlock.”

But, as sweeping as M.B.S.’s economic and cultural reforms may be, he has expressed no interest in liberalizing the country’s political system. Indeed, the model that seems to best conform to his vision is China, with its dynamic economy, literate population, and authoritarian rule. Experts on the Saudi system, including those who admire M.B.S., say that his efforts are being carried out with one overriding goal: to preserve the House of Saud.

As M.B.S. neared the end of his first year as crown prince, his position seemed secure. He had eliminated or silenced nearly all potential opposition to his rule. He replaced the generals in charge of the war in Yemen and pushed ahead with his plans to privatize Saudi Arabia’s oil industry.

At the same time, the waves of arrests created a climate of fear in which even the tamest criticism of the government was labelled disloyal. His purges of rivals, and his creation of what amounted to a cult of personality, appeared designed to place on M.B.S. the entire burden of governing and to leave the country’s institutions enfeebled. His rapid modernization and anti-corruption initiatives, whatever their motivations, seemed sure to inspire legions of enemies. Still, his supporters in both Washington and Riyadh feel that, whatever his faults, the alternative would be worse.

In the White House, Kushner’s power has been diminished, as his security clearance was revoked amid a series of scandals. But the appointments of Mike Pompeo as Secretary of State and John Bolton as national-security adviser presage an even more hawkish era, in which there will be few constraints on M.B.S.’s regional ambitions. “No one would have thought that the Saudi leader could take on the royal family, the clerical establishment, and the country’s most powerful businessmen, but he did,” a former American official who has dealt with M.B.S. told me. “But success at home convinced him he could get away with the things he did abroad. M.B.S. has always had a combination of vision, hubris, and arrogance, all of which are now playing out. What troubles me about M.B.S. is, he learns from his successes, but not his failures. That’s the danger.” ♦

An earlier version of this piece misstated the reach of the Safavid Empire. It also misstated the proposed location of the U.S. Embassy in Israel.