Polish history begins, like that of Russia, with Scandinavian invasion; Szainocha, a reliable authority of the present century, asserted that the Northmen descended on the Polish coast of the Baltic, and became, as in Russia, ancestors of the noble houses. On the other hand, it is on record that the first Grand Duke of Poland (about A. D. 842), was Piastus, a peasant, who founded a dynasty that was superseded only in 1385 by the Lithuanian Jagellons. Christianity was introduced by the fourth of the Piasts, A. D. 964, and it was a sovereign of the same House, Boleslas I., the Brave, who gave a solid foundation to the Polish State. He conquered Dantzig and Pomerania, Silesia, Moravia, and White Russia, as far as the Dnieper. After being partitioned, in accordance with the principle that long obtained in the neighbouring Russian principalities, the component territories of Poland were reunited by Vladislaf (Ladislaf) the Short, who established his capital, in 1320, at Cracow, where the Polish kings were ever after crowned. Casimir the Great, the Polish Justinian (1334-1370), gained for himself the title of _Rex Rusticorum_, by the bestowal of benefits on the peasantry, who were _adscripti glehoe_, and by the limitation of the power of the nobles, or freeholders. On his death, Louis, King of Hungary, his sister's son, was called to the throne; but in order to insure its continued possession he was compelled to reinstate the nobles in all their privileges, under a _Pacta Conventa_, which, subject to alterations made at Diets, was retained as part of the Coronation Oath so long as there were Polish kings to be consecrated. He was the last sovereign of the Piast period. After compelling his daughter to marry, not William of Austria, whom she loved, but Jagellon, Duke of Lithuania, who offered to unite his extensive and adjacent dominions with those of Poland, and to convert his own pagan subjects to Christianity, the nobles, in virtue of their Magna Charta, elected Jagellon (baptized under the name of Ladislas) to the throne of Poland, which thus became dynastically united (1386), with that of Lithuania.