Game of Thrones: What We Know About Saudi Arabia's Next King Mohammed Bin Salman

King Salman, the 81-year-old ruler of Saudi Arabia, elevated his son, Mohammed bin Salman, to the role of crown prince on Wednesday, meaning that the 31-year-old is now the next in line to the Saudi throne.

Salman, often referred to by his initials 'MBS', has leapfrogged the king's nephew Mohammed bin Nayef, who has been unexpectedly demoted. When Mohammed takes over from his father it will be the first time in the kingdom's history that the top job has been held by someone other than a son of Saudi Arabia's founder, Ibn Saud.

The move marked another step in the meteoric rise of the young prince, who is already the world's youngest defense minister and has been charged with overhauling the country's economy. Mohammed bin Salman oversees the state oil company, which is crucial to the Gulf kingdom's economy, and has introduced social reforms such as restrictions on Saudi Arabia's religious police.

The eldest son of Salman's third and most recent wife, Mohammed bin Salman has eclipsed his three older half-brothers from the king's first wife and is widely seen as his father's closest advisor.

Born in Jeddah in 1985, Mohammed bin Salman holds a law degree from King Saud University and, unlike many Saudi royals, has never been educated outside the country. He entered politics in 2009, serving as a special advisor to his father when Salman was the governor of Riyadh Province. Ever since, he has gained a slew of new titles.

But it has not been all plain sailing for the young prince. As minister of defense, Mohammed bin Salman has led Saudi Arabia's bloody war in neighboring Yemen since March 2015, where Riyadh is fighting against Iranian-backed Houthi rebels to reinstate the government of exiled President Abed Rabbo Mansour Hadi.

Rights groups have slammed Saudi Arabia for using cluster munitions —widely banned in the international community—in its bombing campaign and for contributing to a major humanitarian crisis in Yemen, which has left 14.1 million people in need of urgent food assistance.

Despite the criticism, Riyadh has kept up the pressure on the Houthis and has even courted Washington for additional military assistance.

Read more: Saudi prince approves of Trump's views on Islam and his travel ban

Under Mohammed bin Salman's leadership, Saudi Arabia has also continued to play a key proxy role in the war in Syria, arming anti-government rebels, some of which are accused of links to Al-Qaeda. The young prince also spearheaded the creation of a coalition of dozens of Islamic countries to fight terrorism in late 2015.

Mohammed bin Salman and Trump
U.S. President Donald Trump meets with Mohammed bin Salman, deputy crown prince and minister of defense of the kingdom of Saudi Arabia, in the Oval Office at the White House on March 14. Bin Salman has been promoted by his father to be next in line to the Saudi throne. Mark Wilson/Getty

He is also rumoured to be the chief proponent of the current impasse between Saudi Arabia and Qatar, under which Riyadh and its allies the UAE and Egypt have imposed a blockade on the tiny island state after accusing it of supporting terrorist groups.

Mohammed bin Salman has also emerged as a trusted envoy for his father. It was the deputy crown prince who was sent to Washington in March to meet with President Donald Trump in a head-to-head that preceded Trump's visit to the kingdom in May. The Saudi prince "expressed his satisfaction" after the meeting and commended Trump for his clarifying "his views on Islam," in spite of various controversial statements and actions taken by Trump towards Muslims on the campaign trail and while in office.

The prince's promotion is another sign that the current Saudi king is bucking long-held tradition in the Gulf state. Traditionally, the line of succession in Saudi Arabia has passed from brother to brother: King Salman came to the throne in 2015 after the death of his half-brother, Abdullah, and originally appointed his own half-brother, Muqrin bin Abdulaziz, as crown prince.

But after a tenure of just three months, Salman replaced Muqrin with Mohammed bin Nayef, his nephew, to the role. Now, with Mohammed bin Salman's appointment, the king has once again changed how power will pass down in the conservative Islamic kingdom.