There were several strong tribes but after some time of fight for power the tribe called "Polanians" (or "Polans" or in Polish Polanie) came into prominence. In the middle of the 9th century they started massive expansion to the neigbouring territories and consequently pushed away Popielid dynasty. They gained considerable power and were able to take under their rule vast areas of land. From that period emerges one single ruler Mieszko I of [Piast dynasty]? (born ca 930 AD). The real Poland's sovereign state history begins with him. Soon he married a Czech princess Dobrava and accepted Christianity for himself and his kingdom in 966 AD.