The last time religious aggression swept an entire subcontinent was during the Reformation four centuries ago, when Christians hashed out their hatreds much as Muslims of the Middle East are doing today.
Islamic State, or as the president calls it, the Islamic State in Iraq and the Levant, is fighting to restore a caliphate. Catholics and Protestants spent decades warring over similar issues. Should all Christians accept the same religious doctrine? Should all nations be under the dominion of the pope?
Sunnis bowed to a caliph who ruled over all believers regardless of nationality. The last caliph was Sultan Abdülmecid II. Kemal Ataturk, the resolute builder of modern Turkey, fired Abdülmecid in 1924. The 400-year-old caliphate in Istanbul vanished.
Unsurprisingly, not everyone was happy about the rupture. In 1928, the Muslim Brotherhood began in Egypt. That group and other like-minded sectarian organizations gradually spread into the new secular nations of Syria, Jordan, Iraq and Iran.