In modern Polish, "Mińsk" without an attribute usually refers to the city in Belarus, which is about 50 times bigger than Mińsk Mazowiecki; (cf. Brest-Litovsk and Brześć Kujawski for a similar case). The area of today's Minsk was settled by Lithuanians in the 9th and 10th centuries AD. The Svislach River valley was the settlement boundary between two Early East Slav tribes – the Krivichs and Dregovichs. By 980, the area was incorporated into the early medieval Principality of Polotsk, one of the earliest East Slav principalities of Old Rus' state. Minsk was first mentioned in the name form "Měneskъ" (Мѣнескъ) in the Primary Chronicle for the year 1067 in association with the Battle on the River Nemiga. 1067 is now widely accepted as the founding year of Minsk. City authorities consider the date of 3 March 1067, to be the exact founding date of the city, though the town (by then fortified by wooden walls) had certainly existed for some time by then. The origin of the name is unknown but there are several theories. In the early 12th century, the Principality of Polotsk disintegrated into smaller fiefs. The Principality of Minsk was established by one of the Polotsk dynasty princes. In 1129, the Principality of Minsk was annexed by Kiev, the dominant principality of Kievan Rus; however in 1146 the Polotsk dynasty regained control of the principality. By 1150, Minsk rivaled Polotsk as the major city in the former Principality of Polotsk. The princes of Minsk and Polotsk were engaged in years of struggle trying to unite all lands previously under the rule of Polotsk. Minsk escaped the Mongol invasion of Rus in 1237–1239. In 1242, Minsk became a part of the expanding Grand Duchy of Lithuania. It joined peacefully and local elites enjoyed high rank in the society of the Grand Duchy. In 1413, the Grand Duchy of Lithuania and Kingdom of Poland entered into a union. Minsk became the centre of Minsk Voivodship (province). In 1441, as Grand Duke of Lithuania, Casimir IV included Minsk in a list of cities enjoying certain privileges, and in 1499, during the reign of his son, Alexander I Jagiellon, Minsk received town privileges under Magdeburg law.