The three kingdoms of Poland, Bohemia and Hungary were among the largest in sixteenth-century Europe. Together they filled the area bounded by Germany, the Baltic, Russia and the Balkans, or, in the terms of physical geography, the basins of the Oder, Vistula and middle Danube. They occupied a central position also in respect of political development, for while they lagged behind the western European states they were in advance of Russia and Turkey. It is this central position which constitutes their historical interest: the balance of power between the landowners and the monarchy was so even throughout the century as to give to their relations, whether of conflict or co-operation, a significance that illuminates the more decisive conflicts which were at the same time being waged in the extremer parts of Europe.

The accession of Sigismund I ‘the Old’, of the Jagiellon dynasty, to the Polish throne in 1506, and of Ferdinand I of Habsburg, brother of the Emperor Charles V and already ruler of the complex of the hereditary Austrian lands, to the thrones of Bohemia and Hungary in 1526, may be said to mark the beginning of the conflict, for they both succeeded to fainéant kings against whom the landowners had virtually had things all their own way. The kingdoms to which they acceded were still medieval in the looseness of their political structure. Sigismund’s inheritance was not even in name a kingdom but a rzecz pospolita or respublica; the half-dozen duchies into which the kingdom of Poland had fallen apart in the twelfth century had not yet all been brought under the direct rule of the king, for the duchy of Mazovia was not incorporated until the failure of heirs to its last duke, who died in 1526.