The History of Islam in Africa and accounts of how the religion spread, especially in North and the Horn of Africa, has always been contentious. Head of Awqaf Africa London, Sheikh Dr. Abu-Abdullah Adelabu has written in his Movements of Islam in face of the Empires and Kingdoms in Yorubaland claims about the early arrival of Islam in southwestern Nigeria. He seconded the Arab anthropologist Abduhu Badawi on the argument that the early Muslim missionaries had benefited their works from the fall of Kush in northern Sudan and the prosperity of the politically multicultural Abbasid period in the continent which, according to him, had created several streams of migration, moving west in the mid-9th century into Sub-Saharan Africa. Adelabu pointed at the popularity and influences of the Abbasid Dynasty (750–1258), the second great dynasty with the rulers carrying the title of 'Caliph' as fostering peaceful and prosperous migration of the intercultural Muslims from the Nile Valley to Niger as well as of the Arab traders from the desert to Benue. Adelabu's claim seems to be in line with the conventional historical view that the conquest of North Africa by the Umayyad Caliphate between AD 647–709 effectively ended Christianity in Africa for several centuries. Some argue that adoption of Islam was motivated by the desire to enhance trade, as Islam provided a moral code of conduct to regulate commercial activities, especially with respect to credit and security.