MANSFELD, (PETER) ERNST, GRAF VON

(count of) born 1580, Luxembourg died Nov. 29, 1626, Rakovica, near Sarajevo, Bosnia Roman Catholic mercenary who fought for the Protestant cause during the Thirty Years' War (161848); he was the Catholic League's most dangerous opponent until his death in 1626. An illegitimate son of Peter Ernst, Frst von Mansfeld, governor of the Spanish fortress in Luxembourg, Mansfeld entered the Habsburg army and fought in much of Europe. Although he was legitimized, the stigma of his birth adversely influenced his career, and during the first decade of the 17th century he gradually became an enemy of the house of Austria. At the outbreak of the Thirty Years' War (1618), Mansfeld was in the service of the Protestant Union and, campaigning against the Habsburgs in Bohemia, captured Plzen (Pilsen). He nevertheless failed to support the new Protestant Bohemian king, the elector Palatine Frederick V, who was subsequently defeated at the Battle of the White Mountain (November 1620). For the next two years, however, Mansfeld successfully defended the elector's Rhenish provinces against General Johann Tserclaes, Graf von Tilly, commanding the Catholic forces. By 1623, however, Frederick V's treasury was exhausted. After futile negotiations with Austria and the French Huguenots, Mansfeld and his ally, Christian of Brunswick, marched through Lorraine and Flanders to enter the service of the United Provinces of the Netherlands, conquering and holding East Frisia until 1624. Mansfeld then acquired English subsidies for the entry of Denmark into the war. While Christian IV of Denmark fought Tilly in Lower Saxony, Mansfeld opposed the imperial general Albrecht von Wallenstein at Dessau but was unable to dislodge him. Followed by Wallenstein, Mansfeld then marched to Hungary with a new army in French pay to join forces with Prince Gbor Bethlen of Transylvania, who was fighting the Austrians in the Balkans. Epidemics caused considerable loss to both sides, and, after Gbor Bethlen negotiated separately with Austria, Mansfeld decided to enter the Venetian service; he died on his way toward Venetian territory.