The author deals with the Czech and Polish origo gentis in the medieval historical writing from the oldest chronicles of 12th and beginning of 13th century, when the legends about the origin of both peoples developed separately in Bohemia and in Poland. Since the time of Charles IV, the legends about the origin of both nations began to combine under the political propaganda and territorial ambitions of Charles IV.
The official historiography of the court of Charles IV presented the Poles as descendants of Lech and Krak, brothers of the Czech ancestor Boemus/Czech, accordingly as the relatives of the Czechs. In the 15th century, the Silesians incorporated in those ideas too.