Out of Arabia

In 632 the Prophet Muhammad died at Medina, having united most of the Arabian Peninsula under the new religion of Islam. His death nearly undid everything: many tribes, seeing their allegiance as personal to Muhammad, fell away, and the first caliph, Abu Bakr, had to fight the fierce Ridda ('apostasy') wars to hold the community together. Out of that crucible emerged a unified, militarised Arabia and a formidable instrument of war — and its energies turned outward.

The timing could not have been more perfect. To the north lay the two great empires of the age, Byzantium and Sasanian Persia, and they had just fought each other to utter exhaustion in a twenty-six-year war. Both were bankrupt, their armies wrecked, their frontier provinces devastated and their populations alienated by heavy taxes and religious persecution. Into this vacuum the Arab armies struck.

The Arabs raided first into the borderlands of Persian Iraq, where the brilliant general Khalid ibn al-Walid won a string of victories, then wheeled toward Byzantine Syria. In 634 they invaded Palestine and crushed a Byzantine field army at Ajnadayn — the first great pitched battle between Islam and the Roman Empire. Damascus fell soon after. The conquest had begun, and its speed would astonish the world.