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In 1362 or 1363, Grand Duke Algirdas marched between lower Dnieper and Southern Bug. First, Algirdas captured remaining territories of the Principality of Chernigov – the bulk of the territory, including the capital in Bryansk, fell under Lithuanian control around 1357–1358. The Lithuanians then attacked Korshev (Коршов), an unidentified fortress located in the upper reaches of the Bystraya Sosna River, tributary of the Don River. It is believed that Algirdas further conquered territories of the former Principality of Pereslavl. The area belonged to Crimean ulus which was engaged in a campaign against New Sarai and could not organize effective resistance. Three Tatar beys of Podolia gathered an army to resist the invasion. Lithuanians smashed the Golden Horde forces during the Battle of Blue Waters and stopped its further expansion in the present-day Ukraine. The victory brought the city of Kiev and a large part of present-day Ukraine, including sparsely populated Podolia and Dykra, under the control of the expanding Grand Duchy of Lithuania. The duchy also gained access to the Black Sea. Algirdas left his son Vladimir in Kiev. After taking Kiev, Lithuania became a direct neighbor and rival of the Grand Duchy of Moscow.