The eastern boundary of Poland at this period served also as the western boundary of Russia from the head-waters of the western branch of the river San in the Carpathian Mountains at a point west of Premysl (in the Galicia of to-day) to Brest-Litovsk, from which point the Russian boundary continued toward the northeast till it reached the sea, leaving Pskoff considerably and Yurieff (now Dorpat) slightly to the east,--that is, on Russian territory. Between Russia, north of Brest-Litovsk and Poland, was the irregular triangle composing the lands of Lithuanian and Finnish tribes. From the upper San the Russian boundary southward coincided with the Carpathians, including the territory between the Pruth to its mouth and the Carpathians. This boundary between Poland and Russia, established at that period, corresponds as nearly as possible with the line of demarcation between the two peoples at the present day.
During the two centuries following 1139, Poland continued to lose on the west and the north, and that process was fairly begun through which the Germans finally excluded the Poles from the sea, and turned the cradle of Poland into South Prussia, the name which it bears to-day.
At the end of the fourteenth century a step was taken by the Poles through which it was hoped to win in other places far more than had been lost on the west. Poland turned now to the east; but by leaving her historical basis on the Baltic, by deserting her political birthplace, the only ground where she had a genuine mission, Poland entered upon a career which was certain to end in destruction, unless she could win the Russian power by agreement, or bend it by conquest, and then strengthened by this power, turn back and redeem the lost lands of Pomerania and Prussia.
The first step in the new career was an alliance with Yagello (Yahailo) of Lithuania, from which much was hoped. This event begins a new era in Polish history; to this event we must now give attention, for it was the first in a long series which ended in the great outburst described in this book,--the revolt of the Russians against the Commonwealth.
To reach the motives of this famous agreement between the Lithuanian prince and the nobles and clergy of Poland,--for these two estates had become the only power in the land,--we must turn to Russia.
Lithuania of itself was small, and a prince of that country, if it stood alone, would have received scant attention from Poland; but the Lithuanian Grand Prince was ruler over all the lands of western Russia as well as those of his own people.
What was Russia?
The definite appearance of Russia in history dates from 862, when Rurik came to Novgorod, invited by the people to rule over them. Oleg, the successor of this prince, transferred his capital from Novgorod to Kieff on the Dnieper, which remained the chief city and capital for two centuries and a half. Rurik's great-grandson, Vladimir, introduced Christianity into Russia at the end of the tenth century. During his long reign and that of his son Yaroslav the Lawgiver, the boundary was fixed between Russia and Poland through the places described above, and coincided very nearly with the watershed dividing the two river-systems of the Dnieper and the Vistula, and serves to this day as the boundary between the Russian and Polish languages and the Eastern and Catholic churches.
In 1157 Kieff ceased to be the seat of the Grand Prince, the capital of Russia. A new centre of activity and government was founded in the north,--first at Suzdal, and then at Vladimir, to be transferred later to Moscow.
In 1240 the conquest of Russia by the Tartars was complete. Half a million or more of armed Asiatics had swept over the land, destroying everything where they went. A part of this multitude advanced through Poland, and were stopped in Silesia and Moravia only by the combined efforts of central Europe. The Tartar dominion lasted about two hundred and fifty years (1240-1490), and during this period great changes took place. Russia before the Tartar conquest was a large country, whose western boundary was the eastern boundary of Poland; liberated Russia was a comparatively small country, with its capital at Moscow, and having interposed between it and Poland a large state extending from the Baltic to the Black Sea,--a state which was composed of two thirds of that Russia which was ruled before the Tartar conquest by the descendants of Rurik; a state which included Little, Red, Black, and White Russia, more than two thirds of the best lands, and Kieff, with the majority of the historic towns of pre-Tartar Russia.