The Principality of Opava or Duchy of Troppau was a historic territory split off from the Margraviate of Moravia before 1269 by King Ottokar II of Bohemia to provide for his natural son, Nicholas I. The Opava territory thus had not been part of the original Polish Duchy of Silesia in 1138, and was first ruled by an illegitimate offshoot of the Bohemian Přemyslid dynasty, not by the Silesian Piasts like many of the neighbouring Silesian duchies. Wikipedia