Mieszko I (myĕsh`kô) or Mieczyslaw I (–chĭsläf), c.922–992, duke of Poland (962–92), the first important member of the Piast Piast (pyäst), 1st dynasty of Polish dukes and kings. Its name was derived from that of its legendary ancestor, a simple peasant.
..... Click the link for more information. dynasty. The first German invasions of Poland began in 963. To avert this threat, Mieszko obtained (c.963) a friendly treaty with Holy Roman Emperor Otto I Otto I or Otto the Great, 912–73, Holy Roman emperor (962–73) and German king (936–73), son and successor of Henry I of Germany. He is often regarded as the founder of the Holy Roman Empire .
..... Click the link for more information. , to whom he agreed to pay tribute. Mieszko later conquered Pomerania. In 966 he accepted Christianity and immediately began the conversion of Poland. Late in his reign he placed Poland under the protection of the pope, thus gaining papal support of Polish integrity. His son Boleslaus I Boleslaus I (bō`ləslôs), c.
..... Click the link for more information. succeeded him.

Mieszko I

(born c. 930—died May 25, 992) Prince or duke of Poland (963?–992). He accepted Christianity from Rome (966) to avoid forced conversion by the Germans and the incorporation of Poland into the Holy Roman Empire. He expanded Poland southward into Galicia and northward as far as the Baltic Sea.