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 socially connected primarily by tribal structures. It appears that the elders cooperating with the Duke first felt the need for super-tribal unity, as expansion allowed them to broaden their influence. Mieszko and his people were described around 966 by Abraham ben Jacob, a Sephardi Jewish traveller, who at that time visited the Prague court of Duke Boleslav I the Cruel. Abraham presented Mieszko I as one of the four Slavic "kings", reigning over a vast "northern" area, with a highly regarded and substantial military force at his disposal. More precise contemporary records regarding Mieszko were compiled by Widukind of Corvey,