Mieszko I of Poland mentions a gift or dedication of Mieszko's land to the Pope (the act took place almost a hundred years earlier). It is roughly his borders that Poland was returned to in 1945. There is no certain information on Mieszko I's life before he took control over his lands. Only the "Lesser Poland Chronicle" gives the date of his birth as somewhere between the years 920–931 (depending on the version of the manuscript), however, modern researchers don't recognize the Chronicle as a reliable source. Several historians on the basis of their investigations postulated the date of Mieszko I's birth to have
Mieszko I of Poland expanding and improving the so-called war monarchy system. According to existing sources, Mieszko I was a wise politician, a talented military leader, and a charismatic ruler. He successfully used diplomacy, concluding alliances, first with Bohemia, then Sweden, and the Holy Roman Empire. In foreign policy, he placed the interests of his country foremost, even entering into agreements with his former enemies. On his death, he left to his sons a country with greatly expanded territories, and a well-established position in Europe. Mieszko I also enigmatically appeared as "Dagome" in a papal document dating to about 1085, called "Dagome iudex", which