Mieszko II of PolandMieszko II Lambert, also spelled as Miezko II, was the king of Poland (990 - 1034). He was the son of Boleslaw I Chrobry married Rixa von Lothringen. Their children were Casimir I of Poland, Rixa of Poland, and Gertrude of Poland.
Mieszko II was very educated man for his time. He was able to read and write, and knew both Greek and Latin. He is known (unjustly) as Mieszko Gnuśny which means Lazy, Stagnant or Slothful. He received that name because of his most unfortunate ending of rule; but when he begin, he acted as skillful and talented ruler. Before he became king in 1025, he was probably ruling as father's governor in Krakow, probably since 1013, when he supposedly built many churches.
He waged war against Germany (starting in 1028), quite successfully: he was able to repel the German army, and later he even invaded Saxony. He allied with Hungary, and Hungarians even for some time took Vienna. This war probably was because of family connections of Mieszko with opposition against emperor Conrad II in Germany.
To understand what happened later we have to tell a little about Mieszko's family. He had older brother, Bezprym, and younger one, Otton. According to old Slavic custom father should divide his heritage between sons; however kingdoms should not be divided. So Mieszko's brothers receive nothing from father's legacy. What's worse, Bezprym was oldest son so many probably felt that he should be new king. Problem with Bezprym is that he from the beginning was not liked by father, as denoted by his name (Piasts usually used names like Boleslaw, Mieszko, later also Kazimierz, Wladyslaw, or Emperor's names: Otton, conrad, Heinrich: but Bezprym is common name, which implies that Boleslaw don't want him to became new ruler). He was send to monastery, and he was son of unknown Hungarian wife of Boleslaw, who was expelled by him later. Both Mieszko's brothers escaped abroad: Otton to Germany, Bezprym to Kiev Rus. Soon after both German emperor and great duke of Kiev, Yaroslaw the Wise, allied and made simultaneous invasions.
Facing two enemies, Germans from west and Rusins from east, Mieszko escaped to Czech where he was probably castrated. Bezprym started his rule with sending crown and other king's insignia to Germany. Mieszko returned soon, but this time he was forced to pledge allegiance to German Emperor, and Poland was divided between him, his brothers Otton and Bezprym, and some mysterious Thiedric (probably nephew or cousin). Mieszko was able to reunite Poland (Otton was killed by one of his own man). What happened next is great puzzle. Today modern historians are guessing that Mieszko was killed in plot organised by aristocracy (1034). After his death, peasants revolted. Why and when, we don't know exactly.
Casimir I of Poland, son of Mieszko, was either expelled by that uprising, or uprising was caused by expelling by aristocracy. Uprising is called pagan reaction, but modern historians are arguing that it was rather caused by economical issues (huge new taxes for the Church, militarisation of early Polish kingdom: almost all male population server in army etc) than religious. Priests, monks knights were killed, cities, churches and monasteries were burned. Chaos was even greater when suddenly Czechs invaded from the south. land became divided between local rulers, of whom one is known (Maslav, who ruled Masovia). Greater Poland was so devastated, that is ceased to be core of Polish kingdom. New Polish kings moved their capital to Little Poland, to Krakow.
See also: Rulers of Poland