After months abroad in Germany for medical attention Sultan Qaboos of Oman returned to Muscat today. He walked off the plane looking gaunt but determined. Qaboos has been a fixture of Gulf politics for decades, his return comes as neighboring Yemen is collapsing into civil war.

Qaboos was born on November 18, 1940 in Salalah the capital of Oman’s western province Dhofar that borders on Yemen. He is the 14th-generation descendant of the founder of the Al Bu Sa’idi dynasty which created the sultanate in the 1600s after expelling the Portuguese from Muscat. He was educatedin India and the Royal Military Academy at Sandhurst then spent a year with the British Army of the Rhine in Germany. When he returned home to Salalah his father kept him isolated and under virtual house arrest in the palace. The father was notoriously averse to any modernization of the country.

Qaboos came to power in July 1970 in a coup orchestrated by British intelligence using army officers seconded to the Omani army. British officers took control of the palace, lightly wounded the sultan in a short gunfight and then Qaboos’s father was flown out of the country on a Royal Air Force jet never to return. London was convinced regime change was essential because the country was in a civil war with a communist insurgency backed by the Soviets and their then proxy the People’s Democratic Republic of Yemen. The country had only ten kilometers of modern roads, virtually no education or health infrastructure and seemed about to be the next Arab monarchy to collapse.

With British encouragement Qaboos asked the Shah of Iran and King Hussein of Jordan for help. The Iranians sent a regiment of troops and the Jordanians sent advisors. The communist insurgency in Dhofar was defeated and many of its leaders defected to the new government. Qaboos modernized the country, established a parliament and created one of the most stable and well governed countries in the Middle East. Oman had a miniature version of the Arab Spring in 2011 during which the Sultan ordered further reforms to answer calls for change, and demonstrations petered out. The majority of Oman’s four million residents have never known any ruler except Qaboos.

While maintaining special ties to the United Kingdom, Qaboos has also been a close ally of the United State. Oman was the staging base for the ill-fated American hostage rescue mission in 1980 to get the American diplomats home. Oman participated in Operation Desert Storm to liberate Kuwait. Later, Oman became a useful intermediary for sending messages from Washington to Tehran. Most recently, Oman has hosted secret talks between the U.S. and Iran on Iran’s nuclear program.

Last July, the Sultan traveled to his residence in Munich for medical tests. Until today, he has not left Germany since and he missed the Omani National Day (his birthday) celebration for the first time last year since his coup. Secretary Kerry visited Qaboos briefly in Munich in January, but no photos were released of their meeting.

He also failed to travel to Saudi Arabia for King Abdallah’s funeral, a notable omission for a fellow Gulf monarch. He is widely reported to be suffering from terminal cancer. He has barely spoken to the nation since he traveled to Germany giving only a brief address on national day.

The Sultan has no sons and has not publicly designated an heir. The royal family is supposed to choose a successor within three days of the Sultan’s death. If they cannot agree, they are to open a sealed letter that Qaboos has written that contains the name of his choice. The three men believed to be the most likely candidates are the sons of Qaboos’s late uncle, Tariq bin Taimur, who served as the Sultan’s first prime minister. (Qaboos now holds the position himself.) None appears to have been groomed for power: Assad bin Tariq is a Sandhurst-educated businessman; Haitham bin Tariq is Oman’s culture minister; and Shihab bin Tariq led the Navy for fourteen years but retired from the post a decade ago. No successor will have the legitimacy Qaboos has earned.

The royal family has every incentive to make the succession smooth. The country faces two  dangers. Like the other GCC states Oman depends on oil for most of its income but it has relatively small reserves. The decline in oil prices is a much bigger challenge for Oman than for its richer neighbors since it has far smaller financial reserves. 

The more immediate danger is the chaos in Yemen. The collapse of the central government and the advance of pro-Iranian Zaydi Houthi rebels on Aden means Oman faces near anarchy on its sensitive western border. Oman did not send a senior representative to Riyadh last weekend for an urgent GCC meeting on Yemen, perhaps due to Qaboos’ status. The crisis is urgent with Iran expanding its influence and Al Qaeda exploiting the chaos to take control of parts of the lawless country.

Qaboos and any successor will face a long term problem of keeping the Yemeni civil war and its violence from damaging Omani interests. Since Oman sits at the opening of the Straits of Hormuz the whole world has an interest in a stable Oman at this key juncture.