Fahd ascended one of the world's richest thrones in June 1982 during a petrodollar boom, which transformed Saudi Arabia from a poor desert country into a global economic power and pushed its isolated tribal society into the modern world.

He used the huge oil revenues to back Saddam Hussein's Iraq in its eight-year war with Shia Muslim Iran, but when Saddam invaded neighbouring Kuwait, Fahd invited US forces to Saudi Arabia to launch their recapture of the tiny emirate in 1991.

His decision to let half a million non-Muslim fighters into Saudi Arabia, the birthplace of Islam and home to its holiest sites, angered Saudi scholars and a Saudi-born Mujahideen fighter in Afghanistan, Osama bin Laden.

Bin Laden turned against the royal family and its US allies. Ten years later his al-Qaeda network, using mainly Saudi hijackers, carried out the Sept. 11, 2001, attacks which plunged Saudi-US ties, a cornerstone of Fahd's reign, into crisis.

The attacks revealed strains between Fahd's foreign policy, which linked his country inextricably to the world's sole superpower, and the royal family's alliance with largely anti-American and ultra-conservative religious scholars at home.

In 2003, al-Qaeda launched a violent campaign inside Saudi Arabia, targeting Westerners, security forces and oil sites.

By then an ailing King Fahd, weakened and wheelchair-bound after a stroke in 1995, had already passed day-to-day control of the kingdom to his younger half-brother, Crown Prince Abdullah.