But if the clergy were stubborn in their resistence to taxation by the diets, so were the diets in their insistence on such taxation of clerical property. At the Diet of 1525 a revaluation of ecclesiastical property was proposed. The bishops opposed this course resolutely, fearing that a precedent might be established for the diet to tax their tithes. Their fear was not groundless. In 1529 at the Diet of Warsaw the deputies refused to take up the business of the diet until the bishops declared what percentage of their tithes they would give as a contribution to the defense of the country. The bishops strenuously objected on the ground that the nobles did not tax their own incomes but insisted on taxing those of the clergy. The conflict reached a deadlock, and finally the whole question was referred to the king. When at the subsequent diet, called for November 11, 1530, at Piotrków, the Chamber of Deputies moved to impose a tax on the tithes of the clergy, its attempt encountered a determined opposition, not only on the part of the clergy, but also on the part of the king. In consequence of this combined clerical and royal opposition the Chamber developed an equally solid front against the immunities of the church, and demanded the passage of a law taxing the clergy in proportion to the real value of all their property. In case the clergy refused to comply, the deputies threatened to suspend all payments of tithes, and to put the proposed law through and in force at the very next pospolite ruszenie of the szlachta.[429] Nor was this an empty threat. For more than a century and a half, ever since the reign of Casimir the Great (1333-1370), the Polish nobility had chafed under the burden of church tithes. In its relation to the king it was free from all special compulsory taxes for the benefit of the royal treasury, save a nominal tax of two grosze per łan kmiecy, paid in reality by the tenant peasants rather than by the landlords themselves. But in its relation to the church it was not as free. The burden of church tithes rested upon it. Originally voluntary, it became compulsory in the first half of the fifteenth century; and it was a burden that could not be shifted. It was, also, a burden which the clergy never failed to exact.