This paper attempts to reconstruct the events associated with the conflict of 1020-1021, which took place between Yaroslav the Wise, prince of Novgorod and Kyiv, and Bryachislav Izyaslavich, prince of Polotsk. The assumptions was made on the basis of a comparison between the information about this conflict obtained from two different types of documentary sources - Novgorod and Russian chronicles and the Old Icelandic “Eymund's Saga”. The distinctive feature of this work, based on extensive work of the previous researchers, is the author's desire to analyse the history of the conflict between Bryachislav of Polotsk and Yaroslav the Wise focusing on the pre-history of this conflict, the evaluation of the probability and a degree of participation of Ingigerda in it, as well as the specificity of terms of Sudoma’s peace agreement 1021.