By making Interior Minister Mohammed bin Nayef, 55, crown prince and Defence Minister Mohammed bin Salman, 30, deputy crown prince, King Salman has effectively decided the line of succession for decades to come in the world's top oil exporter.

Almost all powers under the king are now concentrated in the hands of the pair, who each chair committees determining all security and economic development issues in Saudi Arabia, and have led Riyadh's month-old campaign of air strikes in Yemen.

In another big shift, Salman replaced veteran Foreign Minister Prince Saud al-Faisal, who had served in the role since October 1975, with the kingdom's Washington ambassador Adel al-Jubeir, the first non-royal to hold the post.

Prince Mohammed bin Nayef, who replaces Prince Muqrin, the successor chosen by the late King Abdullah before his death in January, enjoys closer personal ties with U.S. officials than almost any other senior royal, diplomats have said.

The changes come as Saudi Arabia navigates the messy aftermath of the Arab spring and has departed from decades of backroom politics with its military intervention in Yemen.

 The Yemen move, closely associated with both Prince Mohammeds, is seen by analysts as reflecting a more assertive approach to Saudi Arabia's foreign policy under Salman and his ruling team.

"I think we're going to see a more confrontational policy, faster decision-making and more long-term thinking. A leadership that won't hesitate from any confrontation," said Mustafa Alani, an Iraqi security analyst with close ties to the kingdom's Interior Ministry.

It follows what many Saudis see as a decade of growing Iranian influence across the Middle East and a steady disengagement by Riyadh's historical main strategic partner Washington.

Saudi Arabia also faces long-term domestic challenges, including entrenched youth unemployment, unsustainable state spending and tension between religious conservatives and more Western-oriented liberals.

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