Built to rival the Dome of the Rock in Jerusalem, the great mosque in Damascus has always been claimed by rival faiths Sometime in the mid 1990s, I was standing in the marble courtyard of the Umayyad Mosque in Damascus when two nuns asked me where they could find the head of John the Baptist. I pointed them towards the grand transept facade, gleaming with green and gold mosaics evoking a fertile paradise. Beyond lay the shrine to John or Yahya ibn Zakariyya, as he is known in Arabic, one of the few shared sites of Muslim-Christian pilgrimage. In 2001,...