Among the Italian princes, the Pope naturally supported the cause of the Church of which he was the head. He had sent subsidies to Matthew from the beginning of the Bohemian revolution, but now that the decisive moment seemed near he increased his efforts. He imposed a tithe on all Church property in Italy, and was thus able to forward large sums, not only to Ferdinand, but also to the "Liga" of German Catholic princes whose troops, in 1620, invaded Bohemia. The Grand Duke of Tuscany sent some troops to the aid of the Emperor Ferdinand, and the Duke of Savoy, whose policy had completely changed, also offered to assist him with part of his army.
France did not interfere with armed forces, but the diplomacy of that power was for the moment decidedly favourable to the Emperor. The French envoys dissuaded the Protestant princes of Germany from affording any aid to the King of Bohemia, and the treaty of Ulm, which sealed his fate, was principally due to their efforts.
Turning to Northern Europe, Poland had already, by assisting the Hungarian Catholics in their attack on Bethlen, afforded aid to Ferdinand. During the winter (1619–1620) the Emperor obtained King Sigismund of Poland's permission to enlist a large force of Cossacks on Polish territory. These savage troops spread general terror among the people of Austria and Bohemia, to whom they were known as the "bloodhounds." They specially contributed to the suppression of the Protestant movement in Lower Austria. The King of Denmark, though a Protestant, disapproved of Frederick's expedition to Bohemia, and Gustavus Adolphus, King of Sweden, who appears to have had more sympathy with the King of Bohemia, would by distance alone have been prevented from interfering before the speedy collapse of the Bohemian movement took place. He was also at that moment at war with Poland.
Far more important than the attitude of any of the Powers hitherto referred to, was that of the German princes and towns; for on that the result of the struggle between the competitors for the Bohemian crown principally depended. The German States were at that moment divided into two confederacies: the "Liga," to which most of the Catholics belonged, and the "Union," which—with the exception of Saxony—had been joined by the principal Protestant States. The heads of the two lines of the House of Wittelsbach,
