Frederick had been the first German prince to congratulate the Bohemians on their rebellion, and offer them assistance. In July 1618 he sent a confidential agent to Prague to report upon the state of affairs, and to assure the directors of the support of the Protestant Union, should Spain or Bavaria send help to the Emperor. It was at this juncture that Charles Emmanuel appeared upon the scene, and offered through the Elector Palatine to send Mansfeld with two thousand men at once to the assistance of the Bohemians, if it could be made to appear that the troops were sent by the Elector himself. Frederick at once agreed. [Sidenote: =Mansfeld sent to assist the Bohemians.=] The real truth was known only to the Elector Palatine, Christian of Anhalt, and the margrave of Anspach, and when Mansfeld arrived at the scene of war in September 1618, and formed the siege of Pilsen, all the world believed that he was acting on behalf of Frederick, and many concluded that the Elector would not have dared to take so serious a step, unless he had reason to reckon on the support of England. The relief was well-timed, but the arrangement was not very creditable to any of the parties concerned, for Mansfeld, though an able soldier, was one of that class of military adventurers ever bred in times of war to be the bane and scourge of the helpless and inoffensive people. To put such a man in command, at the beginning of a national struggle, was to stamp it at once as a war of brutality and plunder. [Sidenote: =Further assistance sent from Silesia.=] His arrival, however, at Pilsen changed the face of affairs. The Silesians hearing the action, as they thought, of the Elector Palatine resolved to interfere, and sent three thousand men to the assistance of the Bohemians. Bucquoi in the face of these reinforcements, not only checked his advance on Prague, but was soon obliged to fall back to Budweis, where he was besieged by Thurn. On the 21st of November Pilsen surrendered to Mansfeld, and by the end of the year Budweis with its beleaguered garrison was all that was left to the Emperor of his Bohemian kingdom and army. [Sidenote: =Death of Matthias. Accession of Ferdinand, 1619.=]