when he saw fit. He fought on the Swedish side in the three days' battle around Warsaw in which Yan Kazimir was defeated. This service was to be rewarded by the independence of Prussia.
Hardly had the scale turned in favor of Poland when the Great Elector assisted Yan Kazimir against Sweden; and in the treaty of Wehlau (1657) Poland relinquished its rights over Prussia, which thus became sovereign and independent in Europe. This most important change was confirmed three years later at the peace of Oliva.
Frederick, son of the Great Elector, was crowned "King in Prussia" at Königsberg in 1701. The Elector of Brandenburg became king in that territory in which he had no suzerain.
At the first division of Poland, Royal Prussia of The Deluge, the territory lying between the Vistula and Brandenburg, went to the new kingdom; and Brandenburg, Pomerania, and Prussia became continuous territory.
The early success of the Teutonic Knights was so great that in the third half century of their rule on the Baltic their power overshadowed Poland, which was thus seriously threatened. Toward the end of the fourteenth century, however (1386), the Poles escaped imminent danger by their union with Lithuania and Russia. Through this most important connection they rose at once from a position of peril to one of safety and power.
This union, brought about through the marriage of the Polish princess Yadviga to Yagyello, Grand Prince of Lithuania, and by exceedingly adroit management on the part of the Polish nobles and clergy, opened to the Poles immense regions of country and the way to vast wealth. Before the union their whole land was composed of Great and Little Poland, with Mazovia (see map); after the union two thirds of the best lands of pre-Tartar Russia formed part of the Commonwealth.
Since Poland managed to place and maintain itself at the head of affairs, though this roused at all times opposition of varying violence in the other two parts of the Commonwealth, the social ideals and political structure of Poland prevailed in Lithuania and Russia, so far as the upper classes were concerned. In Lithuania, by the terms of the union, all were obliged to become Catholic; in different parts of Russia, which was Orthodox, the people were undisturbed in their religion at first; but after a time the majority of
