The selection of 78-year-old Prince Nayef to succeed Prince Sultan as the new crown prince of Saudi Arabia ushers in the beginning of what promises to be a season of big changes at the top of the royal family and cabinet, all set in the midst of the Arab awakening. The stakes for the United States are huge, which explains the high-powered delegation sent to Sultan’s funeral including Vice President Joe Biden, Senator John McCain and Director of Central Intelligence David Petraeus.

Sultan was crown prince and minister of defense and aviation. He held the latter post since 1962, making him the longest-serving defense minister in the world. During his half century in government, he amassed a fortune estimated by Saudi sources at over $270 billion. He built the modern Saudi military and concluded some of the largest arms sales in history—with America, Britain and China, among others. His ministry led the talks on the most recent U.S.-Saudi deal that is worth $60 billion to the American defense industry.

Nayef has been minister of the interior since 1975 and has for the moment decided to keep both hats. Day-to-day running of the ministry will be done by his very capable son, Muhammad bin Nayef, who has been the target of repeated al-Qaeda assassination plots. The new crown prince is very close to the country’s Wahhabi clerical establishment and has long been among the most skeptical in the family about reforming the country to allow greater freedom for women, Shia and any form of dissidence. There is little in his career to date to suggest he will open up the country’s absolute monarchy to any kind of reformist political process.

King Abdullah bin Abdul Aziz is in poor health. He attended Sultan’s funeral in a wheelchair, wearing a medical mask to protect against infection. Just before his brother’s death, the family had put out a photo of the king, surrounded by his cabinet, to show he was in charge. Abdallah was seated in a hospital bed with a blanket on him and no hat. Not the image of a robust leader. So Nayef may become king sooner rather than later.

That would mean another succession for the crown prince job. Nayef’s brother Salman bin Abdul-Aziz al-Saud, the governor of the capital Riyadh, is probably next in line, but his health is in question too. The youngest of the surviving sons of the modern kingdom’s founder, Abd al-Aziz, is the intelligence chief Prince Muqrin.

The powerful post of defense minister must be filled sooner. The odds favor Sultan’s eldest son, Khaled, but he is not a certainty. He was commander of the coalition forces that liberated Kuwait in 1991 and his father’s deputy at the Ministry of Defense and Aviation. He published a chatty and insightful memoir about his life, entitled Desert Warrior, that revealed many secrets about the first Gulf War—such as the fact that Israel alerted its nuclear-armed missile forces after Iraq started firing Scuds at Tel Aviv both to warn the Iraqis not to use chemical warheads and to press Washington to do more to hunt Scuds in western Iraq.

But Khaled also led Saudi forces last year in a campaign in northern Yemen against rebel Houthi tribes, which was not very successful. Saudi losses were high, and the rebels were never defeated. The desert warrior’s reputation suffered.

Saud al-Faysal, the foreign minister, is also in ill health and has long sought to retire. His brother Turki bin Faisal al-Saud is the former intelligence chief and ambassador to both the United States and the United Kingdom. Turki is the usual suspect for moving into the post, but that is also uncertain. He has a habit of saying exactly what he thinks, especially about America’s total support for Israel, which would be a tad undiplomatic but refreshingly honest.

The Kingdom faces unprecedented challenges in the tsunami of the Arab awakening. Old allies like Hosni Mubarak have been swept away; old adversaries like Muammar Qaddafi are also gone. There have been small but significant protests at home. In tiny neighboring Bahrain, the Saudi army has effectively occupied the country to prevent a Shia revolution. In the rest of the Gulf monarchies and in neighboring Jordan, the Saudis are urging a tough line against change.

Yemen is the biggest problem in the Arabian Peninsula. The Saudis have never liked President Ali Abdallah Saleh. In the mid-1990s, Sultan engineered a civil war to try to oust him. When I visited him after the war to brief him on our intelligence estimate of how Saleh had successfully defeated the rebels and even captured expensive fighter jets Sultan had bought for them, he was good-natured but visibly angry at the Yemeni president. Now, despite the demands of the UN and the rest of the world, Saleh won’t go, and the country is descending into chaos. The unrest benefits al-Qaeda and threatens the stability of Saudi Arabia’s southwest.

The Obama administration has occasionally chastised the Kingdom for not letting women drive, but in fact the United States is heavily invested in the Saudi system. It provides stability in the world energy market. It is also an ally against Iran and a generally friendly voice in the Islamic world. The king is often referred to inside the country as the “Custodian of the Two Holy Mosques” for his role in defending Mecca and Medina from infidels; non-Muslims are not permitted in either city, and the role of being guardian of Islam gives the Kindom clout from Senegal to Indonesia.

Obama’s first trip to the Middle East was to Riyadh, a reflection of the importance he and his team rightly give to the Kingdom in regional and global politics. Nayef works with America, but he is also suspicious of America. Back in 2002, he famously expressed doubt that Saudis were involved in the 9/11 plot and suggested it was the work of Zionists. But he also provided the key intelligence that thwarted al-Qaeda’s plot to blow up two airplanes over Chicago last year. The U.S.-Saudi partnership, which dates from 1945 when FDR and Abd al-Aziz forged it in a meeting in the Suez Canal, is a rock upon which our Middle East and Persian Gulf polices have been centered for over a half century.

Bruce Riedel is a senior fellow in the Saban Center for Middle East Policy at the Brookings Institution. A career CIA officer, he has advised four presidents on Middle East and South Asian issues in the White House on the staff of the NSC. He is author of The Search for Al-Qaeda (Brookings Institution Press, 2008) and the forthcoming Deadly Embrace: Pakistan, America and the Future of the Global Jihad (Brookings Institution Press, 2011).