Mieszko I of Poland result of the conflict Silesia was taken over by Poland. However, the annexation of Silesia possibly took place around 985, because during this year the major Piast strongholds in Wrocław, Opole and Głogów were already being built. The issue of the incorporation of Lesser Poland is also not completely resolved. Possibly Mieszko took the region before 990, which is indicated by the vague remark of Thietmar, who wrote of a country taken by Mieszko from Boleslav. In light of this theory, the conquest of Lesser Poland could be a reason for the war, or its first stage. Many historians suggested
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