Roustan or Rustam, is the nickname of Napoleon Bonaparte's famous bodyguard Rustam Razmadze. Rustam was born in Tbilisi, and was considered to be Georgian. Rustam was kidnapped when he was a child and sold as a slave in Cairo. One of the local authorities presented a young slave to General Napoleon Bonaparte in 1798. Thus, Rustam (French form: Roustan) became a bodyguard of Napoleon till 1814, when the former married Mademoiselle Douville in Dourdan, France and refused to follow the Emperor in his exile to Elba.
Mamluks (also Mameluks, Mamelukes) (the Arabic word usually translates as "owned") comprised slave soldiers used by the Muslim caliphs and the Ottoman Empire. On more than one occasion they seized power for themselves.
After being converted to Islam, they were trained as cavalry soldiers. While technically after training they were no longer slaves, they were still obliged to serve the Sultan. They were kept by the Sultan as an outsider force, under their direct command, to use in the event of local tribal frictions. Many Mamluks rose to high positions throughout the empire, including commanderships. Status remained non-hereditary at first and children were strictly prevented from following their fathers. The intensive and rigorous training given to each new recruit helped ensure a great deal of continuity in Mamluk practices.
Read further on Wikipedia about the fascinating history of the Mameluks