The Jewish center in Poland, marked by compactness of numbers and a widespread autonomous organization, seemed, down to the end of the seventeenth century, to be the only secure nest of the Jewish people and the legitimate seat of its national hegemony, which was slipping out of the hands of German Jewry. But in 1648 this comparatively peaceful nest was visited by a storm, which made the Jews of Eastern Europe speedily realize that they would have to tread the same sorrowful path, strewn with the bodies of martyrs, that had been traversed by their Western European brethren in the Middle Ages. The factors underlying this crisis were three: an acute economic class struggle, racial and religious antagonism, and the appearance upon the horizon of Jewish history of a new power of darkness--the semi-barbarous masses of Southern Russia. In the central provinces of Poland the position of the Jews, as was pointed out previously, was determined by the interaction of class and economic forces on the one hand, and religious and political interests on the other, changing in accordance with the different combinations of the opposing factions. While the kings and the great nobles, prompted by fiscal and agrarian considerations, in most cases encouraged the commercial activities of the Jews, the urban estates, the trade and merchant guilds, from motives of competition, tried to hinder them. As for the Catholic clergy, it was on general principles ever on the alert to oppress the "infidels." As far as economic rivalry and social oppression are concerned, the Jews were able to resist them, either by influencing the Polish governing circles, or by combining their own forces and uniting them in a firmly-organized scheme of self-government, which had been conceded to them in so large a measure. At any rate, it was a cultural struggle between two elements: the Polish and the Jewish population, the Christian and the Jewish estates, or the Church and the Synagogue. This struggle was vastly complicated in the southeastern border provinces of Poland, the so-called Ukraina,[120] by the presence of a third element, which was foreign to the Poles no less than to the Jews--the local native population which was Russian by race and Greek Orthodox in religion, and was engaged principally in agriculture.