Peter Ernst, Graf von Mansfeld (; c. 158029 November 1626), or simply Ernst von Mansfeld, was a German military commander who, despite being a Catholic, fought for the Protestants during the early years of the Thirty Years' War. He was one of the leading mercenary generals of the war. Biography Mansfeld was an illegitimate son of Count Peter Ernst von Mansfeld (1517–1604), a member of the comital House of Mansfeld and royal Spanish stadtholder. He was raised in the Catholic faith at his father's palace in Luxembourg. He gained his earliest military experiences during the Long War in Hungary, where his elder half-brother Charles (1543–1595), also a soldier of renown, held a high command in the imperial army. While his brother succumbed to an epidemic within short time, young Ernst stayed at the theatre of war for several years. In the War of the Jülich Succession he served under Archduke Leopold V of Austria, until that prince's ingratitude, real or fancied, drove him into the arms of the enemies of the House of Habsburg. Although he remained a Roman Catholic, from about 1610 he openly allied himself with the Protestant princes, and during the earlier part of the Thirty Years' War he was one of their foremost champions. He was despatched by Charles Emmanuel, Duke of Savoy, at the head of about 2000 men to aid the revolting Bohemians when war broke out in 1618. He took Pilsen, but in the summer of 1619 he was defeated at the Battle of Sablat; after this he offered his services to the Emperor Ferdinand II and remained inactive while the titular king of Bohemia, Frederick V, Elector Palatine of the Rhine, was driven in headlong rout from Prague. Mansfeld, however, was soon appointed by Frederick to command his army in Bohemia, and in 1621 he took up his position in the Upper Palatinate, successfully resisting the efforts made by Tilly to dislodge him. From the Upper Palatinate, he passed into the Rhenish Palatinate. Here he relieved Frankenthal and took Hagenau; then, joined by his commander, the elector Frederick, he defeated Tilly at Wiesloch (25 April 1622) and plundered Alsace and Hesse. However, Mansfeld's ravages were not confined to the lands of his enemies; they were ruinous to the districts he was commissioned to defend. At length, Frederick dismissed Mansfeld's troops from his service. With Christian of Brunswick the count then entered the