One of his sons, Olgerd, succeeded in getting possession of the whole, and then started upon a career of conquest. He first attacked Novgorod, where one of his brothers had taken refuge, and made conquests east and south, until he reached the Black Sea. Although he was a pagan, Simeon the Proud, Grand Duke of Moscow, gave him his daughter; but this did not prevent Olgerd from waging war with Simeon's successors. In 1368, he defeated the Tartars of the Lower Dnieper, and destroyed Cherson in the Crimea. When he died he followed Gedimin's example by dividing his territories among his sons, but one of them, Jagellon, became sole ruler by putting his brothers to flight and his uncle to death. At this time the Russian language was adopted and with it the Greek Church, although Jagellon was still a pagan. When he married Hedwiga, the (p. 081) heiress to the Kingdom of Poland, he embraced the Roman Catholic church; in 1386, he went to Cracow, where he was crowned King of Poland, and soon after gave orders that his people must join the same church, converting them as Vladimir had introduced Christianity among the people of Kief. Jagellon made Cracow his capital. Some time afterwards one of his cousins, Vitovt, raised a revolt against him in Lithuania, and Jagellon was compelled to cede that territory to him. Thus Vitovt became Grand Duke of Lithuania. Vitovt married the sister of Vassili, Grand Duke of Moscow, and extended his domain toward the east. He invaded Smolensk, whose Grand Duke Sviatoslaf, when fighting in Russia, had taken a delight in impaling and burning alive Russian women and children. That savage had been killed in 1387, in a battle with the Lithuanians, and his son had succeeded him. Vitovt, before Smolensk, invited this prince and his brothers to visit him in his tent. They accepted and were warmly received, but when they were ready to depart, they were told that they were prisoners of war. Smolensk was taken by surprise, and pillaged. Vitovt contemplated the conquest of Russia. His territory bordered in the east on Souzdal and Riazan. He had defeated an army of Tartars in the south, and was making preparations for a bold stroke. Collecting an army of Lithuanians, Poles, Russians, and five hundred Knights of the Teutonic Order, he set out from Kief and came upon the Tartar army near Pultowa where, in 1399, he suffered a serious defeat. He recovered from this blow, and after some time began a war with the Teutonic Order which he defeated in 1410, at the battle of the (p. 082) Tannenberg. He thereupon re-annexed the Jmoud country.