The word 'mamluk' means 'owned' or 'belonging to', and was specially applied to white male slaves captured in war or purchased in the market by Arab lords. The Abassid caliphs from Baghdad employed large numbers of these foreign slaves to protect themselves against the increasing power of provincial governors and nomadic Arab tribes. In Egypt a selected group of slaves was trained as a highly skilled military unit under the Ayyubids on the island of Roda on the Nile (near Cairo). The members of this elite corps were called 'Bahri Mamluks' and were responsible for the assassination of the Ayyubid sultan Turanshah, forcefully legitimising their right to govern Egypt (1250 AD). The Mamluk rule constituted two Dynasties, viz. the House of Kalaun and the Circassian Mamluks. However, in 1517 AD the Mamluk army was defeated by the Turks outside the city gates of Cairo. Consequently, Egypt was assimilated in the Ottoman Empire as a mere province and was ruled by a pasha.