Mieszko I of Poland the conspiracy against Otto II was documented in only one source, the chronicles of the monastery in Altaich in its entry for the year 974. The Duke of Bavaria was defeated, and Emperor Otto II regained full power. Shortly afterwards, the young emperor waged a retaliatory expedition against Bohemia, in 978 forcing Duke Boleslav into submission. In 977 Mieszko's wife, Dobrawa, died. At first there were no apparent repercussions, as the Polish ruler had maintained his alliance with Bohemia. In 979 Otto II supposedly attacked Poland. Mention of this event can be found in the "Chronicle of the Bishops of
Mieszko Kazimierzowic "Gesta principum Polonorum" written in the early 12th century, put Mieszko third in order, among his brother. Modern historian, Janusz Bieniak, has supposed that Mieszko was the second son of Casimir I and was older than Władysław Herman, but most scholars disagree with this hypothesis. The date of Mieszko's birth was given by "Rocznik krakowski" (Kraków Annals). This source omitted dates of birth of Mieszko's brothers. Kazimierz Jasiński thought that "Rocznik" was started shortly before Mieszko's birth and this was the reason for absence of his older brothers. Przemysław Wiszewski supposed tha Casimir I chose Mieszko as his successor and