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 Tanglefoot p. 876). This is the oldest preserved record of the Mieszko's nickname in the form of "Plątonogi". From 1146, after the deposition of his father, Mieszko and his family mainly lived in the town of Altenburg in Saxony, which was granted as a temporary possession to Władysław II by his brother-in-law, King Conrad III of Germany. During his time in exile, Mieszko studied in Michaelsberg and Bamberg. However, the supposed temporary exile was, for the deposed High Duke, for good; he died in Altenburg in 1159. His sons continued the fight to recover their inheritance, and finally three years later,