BEIRUT, Lebanon — The new king of Saudi Arabia, Salman bin Abdul-Aziz Al Saud, has spent more than a half-century among the top echelons of one of the world’s most powerful families and is known to serve as mediator and peacekeeper between its often competing factions.

Best known for overseeing the development of the Saudi capital, Riyadh, during his nearly 50 years as its governor, he became the country’s defense minister in 2011 as a series of uprisings were shaking Arab leaders who had long been Saudi allies.

While Salman is popular inside the kingdom and in the ruling family, he ascended the throne after the death of his brother Abdullah on Friday amid increasing strains on the kingdom.

The drop of world oil prices has hurt the country’s economic base; the jihadists of the Islamic State have questioned its status as the global lodestar of Islam; and new civil strife is shredding Yemen, its southern neighbor.