This book is a study of the evidence that exists to this day in the Niger Republic, and in the adjacent regions of Saharan and non-Saharan Africa, about the life of Sidi Mahmud al-Baghdadi, who, it is believed, introduced new doctrines of Oriental Sufism into the Air Massif during the sixteenth century. The teachings of Sidi Mahmud were to reappear recently in the Khalwatiyya Sufi order ( tariqa) in Niger. They are still important for contemporary Islam in that republic which is a bridge between the Arab world and the Muslim states of the African Sahel. There is also evidence to suggest that initiated members of the Mahmudiyya Sufi order were once to be found throughout the entire Southern Sahara, from Timbuctoo to Borno and Lake Chad. This Sufi order was one of the earliest to be founded in the area of Aïr which was a crossroads of African trade and of rival empires and of conflicting tribes and peoples.