Like a benevolent mother opening her arms to all the children in the neighborhood, Africa held its arms open for successive waves of refugees from Arabia. In turn, the immigrants brought with them the light of Islam and shared it with the people of Africa. This was the quid pro quo between Africa and Arabia: Africa gave protection to the Arabs. In turn, the Arabs shared their faith...

A divided Islamic world offered feeble resistance to the Crusaders who consolidated their hold on the eastern Mediterranean and imposed their fiefdoms on the region. The Seljuks, preoccupied with defending their eastern flank against the Afghan Ghaznavids, had thinned out their western defenses. The pagan Turkish tribes across the Amu Darya on the northeastern frontiers were a constant menace....