From the earliest days, the Crusader States fought to break out of the narrow confines of the Mediterranean coast and conquer the Muslim hinterlands of the Middle East. At first, they could exploit Muslim disunity. Beginning in the middle of the twelfth century, however, the powerful warlord Imad al-Din Zengi unified Syria under his rule. Zengi’s son, Nur al-Din, then became the champion of a holy war—a jihad—against the infidels.