The Wahhabi Movement. The Wahhabi movement (1744-) - its adherents call it the da'wa, 'the call', to pure monotheism - began with one scholar, Muhammad ibn Abd al-Wahhab (1703-1792) of Najd. Preaching a return to the Islam of the first generations, he condemned as idolatry the era's common devotions: pilgrimage to saints' tombs, the veneration of trees and rocks, intercession through the dead, and the mystical excesses of some Sufi orders. Expelled from his home towns, he found in 1744 his protector and partner: Muhammad ibn Saud, emir of Diriyah.
The pact of Diriyah - Saudi sword, Wahhabi creed - powered the First Saudi State's conquests across Arabia, the sack of Karbala (1802), and the occupation and purification of Mecca and Medina (1803-1804), where domes over tombs were demolished - acts that horrified the Ottoman world and provoked Muhammad Ali of Egypt's destruction of Diriyah (1818). The creed survived the state's fall, and returned with the Second Saudi State at Riyadh.
In the 20th century the compact produced its third and enduring state: Abd al-Aziz ibn Saud rebuilt Saudi power with the Ikhwan - settled Bedouin zealots - conquered the Hejaz (1924-25) and its holy cities, and founded the Kingdom of Saudi Arabia (1932), whose constitution remains the Quran and whose religious establishment descends from Ibn Abd al-Wahhab's family (the Al al-Shaykh). Oil wealth after 1945 gave the small Najdi creed global reach: Saudi-funded mosques, schools and literature carried its teachings worldwide.
Wahhabism's influence is one of the great religious facts of the modern age: embraced as authentic reform by many, condemned by other Muslims as intolerant literalism, and entangled - as both inspiration and foil - with the rise of modern Salafism and, at its violent fringe, the jihadist movements the Saudi state itself now fights.