David Nicolle 
Mamluk Askari 1250 1517 [PDF ebook] 

New archaeological material and research underpins this extensive, detailed and beautifully illustrated account of the famous Mamluk Askars who are credited with finally defeating and expelling the Crusaders, halting the Mongol invasion of the Islamic Middle East, and facing down Tamerlane. Probably the ultimate professional soldiers of the medieval period they were supposedly recruited as adolescent slaves, though recent research has begun to undermine this oversimplified interpretation of what has been called the "Mamluk phenomenon".