The Polish policy was more than shortsighted but it was in line with the general attitude of the state. As the upper Dnyeper valley was resettled and as agriculture began to revive, the magnates were able to put forth claims for vast estates. They parcelled out among themselves the new lands as they had done the older lands of Rus’ over which they had assumed control centuries before. They shuddered at the idea that the Sich might embrace all the liberty-loving Ukrainians who were dissatisfied with their harsh rule. The Kozaks were furiously Orthodox. They were zealous supporters of the Orthodox Church. Poland prided itself on its Catholicism and particularly after the successful work of the Jesuits and the establishment of the Church Union, the Polish leaders did not want to do anything that would revive the Orthodox Church. The very existence of the Sich was a direct challenge to all for which the Polish state, with its theories of the equality of the szlachta and its religious interests, stood. The more the Sich became organized and turned from a handful of bold frontiersmen into a definite military force, the more it became the mouthpiece of the Ukrainian population and a refuge for them against oppression. The more it protected the Dnyeper valley and the regions to the east, the more it became a menace and a problem to the Polish rulers. The free republic of the warriors of the Sich was the direct antithesis of the aristocratic life of the great estates which were known throughout Europe for their luxury and their culture. There was more than this involved. The Kozaks, though nominal subjects of the King of Poland, maintained full freedom to harry the Turks and Tatars at will. Every spring, with almost unfailing regularity, they set out on expeditions down the Dnyeper to attack the Turkish and Tatar settlements on the shores of the Black Sea. They invaded Wallachia and Moldavia and interfered in the civil wars that were raging intermittently in both lands. They constantly attacked Ochakiv and plundered almost at will whatever city they wished to. They rescued thousands of Christian Slavs from the Crimean slave mart of Kaffa.