The proximity of nomadic Asia for a time greatly weakened the influences of the proximity of another neighbor—the Black Sea. The Black Sea was, for the Ukraine, the means of intercourse with Byzantium, the greatest cultural center of Europe in the Middle Ages. The Ukraine, because of its waterways, was nearest to Byzantium of all the European countries. This comparatively short period in which the Ukraine was able to maintain intercourse with Byzantium, without obstacles, brought the Ukraine splendid cultural advantages. In a wide stream the Byzantine material and spiritual culture flowed into the Ukraine, so that the country from the 11th to the 13th Century stood highest, culturally, among all the Slavic states and almost equalled the Western European states. In some respects the Ukraine of those days was even superior to Western Europe. In those days Kiev or Halich surpassed London or Paris in wealth and commercial importance. The relations with the sea and with Byzantium kept growing ever more difficult for the Ukraine to maintain, however, as a result of the ever growing pressure of the nomad hordes. Finally, in the 13th Century, came the Tatar invasions. These have best demonstrated the significance of the geographical situation of the Ukraine. The ancient Ukrainian state had to be the first to withstand the Mongol attack. After the defeat, the Ukraine was the first of all the countries of Europe to be desolated by fire [214]and sword. It is true that the strong resistance of the Ukraine effectively stopped the Tatar pressure, and Europe has this circumstance to thank for its escape from the fate of Asia in the 13th Century, three-fourths of which was conquered by the Mongols of Djingis Khan. The Ukrainian state fought a whole century longer with the Tatars, but could not hold their own after that. The Ukraine was systematically devastated by the Tatars, and in the struggle with them the entire military power of the Ukraine was spent. At the same time the neighbors on the north and west—the Poles and Lithuanians—were able to develop freely behind the protecting back of the Ukraine, and to increase their powers. Finally the Poles annexed Eastern Galicia, and the rest of the Ukrainians faced the choice of either joining themselves to the Lithuanians, whose upper classes were at that time, culturally, entirely Ukrainian, or to place themselves beneath the Muscovite yoke. They chose the first. In 1569 the Lublin Union joined the Ukraine to Poland. All these things are the unhappy results of the geographical situation of the land on the threshold of Europe and Asia.