FREDERICK I. (c. 1123-1190), Roman emperor, surnamed "Barbarossa" by the Italians, was the son of Frederick II. of Hohenstaufen, duke of Swabia, and Judith, daughter of Henry IX. the Black, duke of Bavaria. The precise date and place of his birth, together with details of his early life, are wanting; but in 1143 he assisted his maternal uncle, Count Welf VI., in his attempts to conquer Bavaria, and by his conduct in several local feuds earned the reputation of a brave and skilful warrior. When his father died in 1147 Frederick became duke of Swabia, and immediately afterwards accompanied his uncle, the German king Conrad III., on his disastrous crusade, during which he greatly distinguished himself and won the complete confidence of the king. Abandoning the cause of the Welfs, he fought for Conrad against them, and in 1152 the dying king advised the princes to choose Frederick as his successor to the exclusion of his own young son. Energetically pressing his candidature, he was chosen German king at Frankfort on the 4th or 5th of March 1152, and crowned at Aix-la-Chapelle on the 9th of the same month, owing his election partly to his personal qualities, and partly to the fact that he united in himself the blood of the rival families of Welf and Waiblingen. The new king was anxious to restore the Empire to the position it had occupied under Charlemagne and Otto the Great, and saw clearly that the restoration of order in Germany was a necessary preliminary to the enforcement of the imperial rights in Italy. Issuing a general order for peace, he was prodigal in his concessions to the nobles. Count Welf was made duke of Spoleto and margrave of Tuscany; Berthold VI., duke of Zaehringen, was entrusted with extensive rights in Burgundy; and the king's nephew, Frederick, received the duchy of Swabia. Abroad Frederick decided a quarrel for the Danish throne in favour of Svend, or Peter as he is sometimes called, who did homage for his kingdom, and negotiations were begun with the East Roman emperor, Manuel Comnenus. It was probably about this time that the king obtained a divorce from his wife Adela, daughter of Dietpold, margrave of Vohburg and Cham, on the ground of consanguinity, and made a vain effort to obtain a bride from the court of Constantinople. On his accession Frederick had communicated the news of his election to Pope Eugenius III., but neglected to ask for the papal confirmation. In spite of this omission, however, and of some trouble arising from a double election to the archbishopric of Magdeburg, a treaty was concluded between king and pope at Constance in March 1153, by which Frederick promised in return for his coronation to make no peace with Roger I. king of Sicily, or with the rebellious Romans, without the consent of Eugenius, and generally to help and defend the papacy.