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 III the Old of the rebels and divided Henry's Duchy in three parts: Wiślica Land was taken by Casimir, Bolesław took Sandomierz proper, and the rest was led to Mieszko. In 1172 another conflict arose among the Silesian Piasts, when Duke Bolesław the Tall chose to ignore the claims of his first-born son, Jaroslaw by designating his son of the second marriage Henry I the Bearded his sole heir. When Jarosław, forced to become a priest, had returned from his German exile, he claimed a share of the Silesian lands. Mieszko III supported his grandnephew in his demands, and the civil war was