Probably in the middle of the 10th c., in the territories of the present Suwałki Region, Eastern Masuria and south-western Lithuania, the first settlement structures were created, connected with the activity of a group of warriors under the leadership of Jatviag, known from the Nestor Chronicle. They were severely weakened or partially destroyed by the invasions of the rulers of Ruthenia at the end of the 10th c. and in the first half of the 11th c. After a short break, probably due to settlement from the Letto-Lithuanian territories, the old settlement centers were rebuilt and new ones were built. In the 12th and 13th c., historical sources record an increase in the military activity of the Yatvings towards their neighbors. At the same time, social and territorial structures and centers of power developed. At the end of the 13th c., Ruthenian, Polish and Teutonic warfare interrupted the process that could have led Yatvingia to the creation of its own state organization.