ポーランド王国で貴族はいつ発生しだした
The history of Poland has its roots in the migrations of Slavs, who established permanent settlements in the Polish lands during the Early Middle Ages. The first ruling dynasty, the Piasts, emerged by the 10th century AD. Duke Mieszko I (d. 992) is considered the "de facto" creator of the Polish state and is widely recognized for the adoption of Western Christianity that followed his baptism in 966. Mieszko's duchy of Poland was formally reconstituted as a medieval kingdom in 1025 by his son Bolesław I the Brave, known for military expansion under his rule. Perhaps the most successful of the Piast kings was the last one, Casimir III the Great, who presided over a brilliant period of economic prosperity and territorial aggrandizement before his death in 1370 without male heirs. The period of the Jagiellonian dynasty in the 14th–16th centuries brought close ties with the Grand Duchy of Lithuania, a cultural Renaissance in Poland and continued territorial expansion that culminated in the establishment of the Polish–Lithuanian Commonwealth in 1569. 
992