History of Poland 

The history of Poland spans over a thousand years, from medieval tribes, Christianization and monarchy; through Poland's Golden Age, expansionism and becoming one of the largest European powers; to its collapse and partitions, two world wars, communism, and the restoration of democracy.
The roots of Polish history can be traced to ancient times, when the territory of present-day Poland was settled by various tribes including Celts, Scythians, Germanic clans, Sarmatians, Slavs and Balts. However, it was the West Slavic Lechites, the closest ancestors of ethnic Poles, who established permanent settlements in the Polish lands during the Early Middle Ages. The Lechitic Western Polans, a tribe whose name means "people living in open fields", dominated the region, and gave Poland - which lies in the North-Central European Plain - its name.
The first ruling dynasty, the Piasts, emerged in the 10th century AD. Duke Mieszko I is considered the de facto creator of the Polish state and is widely recognized for his adoption of Western Christianity in 966 CE. Mieszko's dominion was formally reconstituted as a medieval kingdom in 1025 by his son Bolesław I the Brave, known for military expansion under his rule. The most successful and the last Piast monarch, Casimir III the Great, presided over a 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 Lithuania, a cultural Renaissance in Poland and continued territorial expansion as well as Polonization that culminated in the establishment of the Polish-Lithuanian Commonwealth in 1569, one of Europe's largest countries.