The Polish clergy’s privileged character respecting their participation in public responsibilities and burdens constituted the most sensitive point of difference between the Polish szlachta and the Polish Roman Catholic clergy.[409] According to Casimir’s Code the duty of participation in the country’s defense rested upon all hereditary estates of the Polish knighthood, regardless of the fact as to whether any of their owners happened to belong at a particular time to the ranks of the clergy or not.[410] Moreover, it was very early established that lands newly acquired by the church were subject to military service. A statute of 1437 provided that all church lands acquired by purchase within the last forty years and those that might be thus acquired in the future were required to render military service.[411] But throughout the fifteenth century the owners of these lands were clever and successful enough in evading these provisions and in maintaining the principle of their freedom from participation in the country’s defense. In 1506 at the Diet of Lublin they even succeeded in securing royal sanction of their freedom from rendering military service due from these lands. Gradually, contrary to the law of Casimir the Great, they extended this principle of their exemption from military service even to their hereditary lands and to village mayorships purchased by them.[412] Naturally, the Polish szlachta rose in arms. It demanded that the mayors of ecclesiastical villages render military service as did the mayors of secular villages; that if the clergy objected, they should produce their privileges exempting the mayors of their villages from that public duty; that the Diet should prohibit the clergy from buying village mayorships; that all newly acquired ecclesiastical lands should be sold to the nobility, which was bearing the burden of public defense; that the clergy be placed on the same footing with the secular nobility in respect of participation in public defense; that their lands be secularized and the income from them be used for purposes of public defense; and that the clergy assume their fair share of special taxes levied by the diets. To be sure, all these demands were not made at once; but they were all made with varying insistence in the course of the first three-quarters of the sixteenth century.