OLGIERD (d. 1377)  , grand-duke of Lithuania, was one of the seven sons of Gedymin, grand-duke of Lithuania, among whom on his death in 1341 he divided his domains, leaving the youngest, Yavnuty, in possession of the capital, Wilna, with a nominal priority . With the aid of his brother Kiejstut, Olgierd in 1345 drove out the incapable Yavnuty and declared himself grand-duke . The two and thirty years of his reign (1345—1377) were devoted to the development and extension of Lithuania, and he lived to make it one of the greatest states in Europe . Two factors contributed to produce this result, the extraordinary political sagacity of Olgierd and the life-long devotion of his brother Kiejstut . The Teutonic knights in the north and the Tatar hordes in the south were equally bent on the subjection of Lithuania, while Olgierd's eastern and western neighbours, Muscovy and Poland, were far more frequently hostile competitors than serviceable allies . Nevertheless, Olgierd not only succeeded in holding his own, but acquired influence and territory at the expense of l=oth Muscovy and the Tatars, and extended the borders of Lithuania to the shores of the Black Sea . The principal efforts of this eminent empire-maker were directed to securing those of the Russian lands which had formed part of the ancient grand-duchy of Kiev . He procured the election of his son Andrew as prince of Pskov, and a powerful minority of the citizens of the republic of Novgorod held the balance in his favour against the Muscovite influence, but his ascendancy in both these commercial centres was at the best precarious . On the other hand he acquired permanently the important principalities of Smolensk and Bryansk in central Russia . His relations with the grand-dukes of Muscovy were friendly on the whole, and twice he married orthodox Russian princesses; but this did not prevent him from besieging Moscow in 1368 and again in 1372, both times unsuccessfully . Olgierd's most memorable feat was his great victory over the Tatars at Siniya Vodui on the Bug in 1362, which practically broke up the great Kipchak horde and compelled the khan to migrate still farther south and establish his headquarters for the future in the Crimea . Indeed, but for the unceasing simultaneous struggle with the Teutonic knights, the burden of which was heroically borne by Kiejstut, Russian historians frankly admit that Lithuania, not Muscovy, must have become the dominant power of eastern Europe .

Olgierd died in 1377, accepting both

Christianity and the tonsure shortly before his death . His son Jagiello ultimately ascended the Polish throne, and was the founder of the dynasty which ruled Poland for nearly 200 years . See Kazimierz Stadnicki, The Sons of Gedymin (Pol.) (Lemberg, 1849—1853) ; Vladimir Bonifatevich Antonovich, Monograph on the History of Western Russia (Rus.), vol. i . (Kiev, 1885) . (R . N .