Muhammad, and instructed them to keep and study it. They were required to swear their oaths to the sultan upon this book, and even encouraged to take their copies of it into battle. This was the origin of their popular designation as the 'Abid al-Bukhari or "Slaves of al-Bukhari". History Isma'il's reign Isma'il, or Moulay Isma'il, ruled as sultan for 55 years between 1672 and 1727, one of longest reigns in Moroccan history. Ruling from a new capital at Meknes, he distinguished himself as a ruler who wished to establish a unified Moroccan state as the absolute authority in the land, independent of any particular group within Morocco – in contrast to previous dynasties which relied on certain tribes or regions as the base of their power. He succeeded in part by creating a new army composed of slaves whose loyalty would be to him alone. In 1699, he gave orders to enslave all black Africans in Morocco, even those who were born free or who were Muslim, and, consequently, he violated two of the central tenets of Islamic law concerning slavery. Moroccan registers show that Isma‘il enslaved over 221,000 black Moroccans between 1699 and 1705. In a study of these events, scholar Chouki El Hamel argues that Isma'il's efforts to justify these actions generated a potent new form of racist discourse in the region that associated black Africans with slavery. The idea of a professional army composed of slaves who were loyal only to the sultan was inspired by the historical precedents of other Middle Eastern and North African military bodies recruited from slaves. Isma'il's army was inspired in particular by the example of the Janissaries in the Ottoman Empire, to which it is sometimes compared. The ‘Abid al-Bukhari or Black Guard or were mainly in charge of collecting taxes and patrolling Morocco's unstable countryside; they crushed rebellions against Isma‘il's rule not only by dissident tribes but also by Isma‘il's seditious sons, who defected from service as his provincial governors to insurrection as would-be usurpers of his throne. The Black Guard were the personal guard and servants of Sultan Isma‘il, they might have also participated in campaigns against the European-controlled fortress enclaves dotting his empire's coast (such as Tangier, taken over after the English withdrew from it and distressed it in 1684 in response), although tasks of this kind were often allocated to European slaves (called ‘aluj , plural