Saudi state television is reporting that Saudi King Abdullah bin Abdulaziz has died at age 90. "Before the announcement," the BBC relayed, "Saudi television cut to Koranic verses, which often signifies the death of a senior royal."

Abdullah, who had been hospitalized in recent weeks with pneumonia, acceded to the crown in 2005. He became the country's sixth king after serving as Saudi Arabia's de facto ruler following his half-brother King Fahd's debilitating stroke in 1995. Given his age, Abdullah never fully escaped conjecture about the state of his health; rumors that he battled various illnesses followed his every appearance.

The thirteenth of King Abdul Aziz Al-Saud's 37 sons, Abdullah reigned during a particularly tumultuous era in the Middle East, which has been beset by war, terrorism, and ongoing instabilities wrought by the Arab Spring.

Saudi Arabia has found itself in precarious circumstances recently. Once the world's largest producer of oil, it now faces challenges to its dominance as oil prices plunge. The country's interpretation of the strict laws of the Wahhabi sect of Sunni Islam and  its controversial alliance with the United States has made it a target for al-Qaeda (and now ISIS). Meanwhile, Saudi Arabia is desperately trying to keep Iran, its neighbor and arch-foe, from going nuclear, which also at times puts it at odds with Washington.

News of Abdullah's death came shortly after word that the Saudi-backed government in Yemen had collapsed, leaving a weak and unstable country—for now, at least, in the hands of Iran-backed rebels—on the kingdom's southern flank.

More broadly, Abdullah's legacy has been characterized by slow-moving reform. He spoke out against democracy and squelched dissent in his own country, however, as The New York Times notes, he also created a scholarship program that "sent tens of thousands of young Saudi men and women abroad to study at Western universities and colleges."

Following the news of Abdullah's death, the White House released a statement, in which the president remarked on his "genuine and warm friendship" with Abdullah. He added:

King Abdullah’s life spanned from before the birth of modern Saudi Arabia through its emergence as a critical force within the global economy and a leader among Arab and Islamic nations.  He took bold steps in advancing the Arab Peace Initiative, an endeavor that will outlive him as an enduring contribution to the search for peace in the region.  At home, King Abdullah's vision was dedicated to the education of his people and to greater engagement with the world.

Assuming the throne on Friday was Saudi Arabian Crown Prince Salman, who is Abdullah's half-brother, although he is nearly 80 years old and rumored to suffer from dementia. Second in line is Abdullah's youngest brother, Prince Muqrin, who, at nearly 70, highlights a bigger problem with the Saudi line of succession. "Sooner or later, of course, the crown will have to move to the next generation," Joshua Keating remarked on Slate.

In the meantime, Salman has become an increasingly visible stand-in for Abdullah over the past few years; he already serves as Saudi Arabia’s deputy prime minister and defense minister.