In addition to the numerous works which treat of the outbreak of the Thirty Years' War see A. Gindely, _Friedrich V. von der Pfalz_ (Prague, 1884); J. Krebs, _Die Politik der evangelischen Union im Jahre 1618_ (Breslau, 1890-1901); M. Ritter, "Friedrich V.," in the _Allgemeine deutsche Biographie_, Band vii. (Leipzig, 1878); and _Deutsche Lieder auf den Winterkoenig_, edited by R. Wolkan (Prague, 1899). FREDERICK I. (1369-1428), surnamed "the Warlike," elector and duke of Saxony, was the eldest son of Frederick "the Stern," count of Osterland, and Catherine, daughter and heiress of Henry VIII., count of Coburg. He was born at Altenburg on the 29th of March 1369, and was a member of the family of Wettin. When his father died in 1381 some trouble arose over the family possessions, and in the following year an arrangement was made by which Frederick and his brothers shared Meissen and Thuringia with their uncles Balthasar and William. Frederick's brother George died in 1402, and his uncle William in 1407. A further dispute then arose, but in 1410 a treaty was made at Naumburg, when Frederick and his brother William added the northern part of Meissen to their lands; and in 1425 the death of William left Frederick sole ruler. In the German town war of 1388 he assisted Frederick V. of Hohenzollern, burgrave of Nuremberg, and in 1391 did the same for the Teutonic Order against Ladislaus V., king of Poland and prince of Lithuania. He supported Rupert III., elector palatine of the Rhine, in his struggle with King Wenceslaus for the German throne, probably because Wenceslaus refused to fulfil a promise to give him his sister Anna in marriage. The danger to Germany from the Hussites induced Frederick to ally himself with the German and Bohemian king Sigismund; and he took a leading part in the war against them, during the earlier years of which he met with considerable success. In the prosecution of this enterprise Frederick spent large sums of money, for which he received various places in Bohemia and elsewhere in pledge from Sigismund, who further rewarded him in January 1423 with the vacant electoral duchy of Saxe-Wittenberg; and Frederick's formal investiture followed at Ofen on the 1st of August 1425. Thus spurred to renewed efforts against the Hussites, the elector was endeavouring to rouse the German princes to aid him in prosecuting this war when the Saxon army was almost annihilated at Aussig on the 16th of August 1426. Returning to Saxony, Frederick died at Altenburg on the 4th of January 1428, and was buried in the cathedral at Meissen. In 1402 he married Catherine of Brunswick, by whom he left four sons and two daughters. In 1409, in conjunction with his brother William, he founded the university of Leipzig, for the benefit of German students who had just left the university of Prague. Frederick's importance as an historical figure arises from his having obtained the electorate of