Count Leopold Joseph von Daun (; 24 September 17055 February 1766), later Prince of Thiano, was an Austrian field marshal of the Imperial Army in the War of the Austrian Succession and Seven Years' War.
Early years
Leopold Joseph Maria was born at Vienna, the son of Count Wirich Philipp von Daun (1669–1741) and his wife, Countess Maria Barbara von Herberstein (1675–1735). The Daun noble family originated from the Rhineland and derived its name from the ancestral seat at Daun south of the High Eifel range. He was first cousin of Countess Eleonora Ernestina von Daun, who later married the Marquis of Pombal, the noted Portuguese statesman.
He was intended for the church, but his natural inclination for the army, in which his father and grandfather had been distinguished generals, proved irresistible. In 1718 he served in the War of the Quadruple Alliance in Sicily, in his father's regiment. He had already risen to the rank of Oberst (Colonel) when he saw further active service in Italy and on the Rhine in the War of the Polish Succession (1734–35). He continued to add to his distinctions in the Turkish War of 1737–39, in which he attained the rank of Feldmarschallleutnant (Major-General).
War of the Austrian Succession
In the War of the Austrian Succession from 1740, Daun distinguished himself by the careful leadership which was afterwards his greatest military quality.
In Austria's First Silesian War against Prussia, he was present at Chotusitz and Prague, and led the advanced guard of Khevenhüller's army in the victorious Danube campaign of 1743. Field Marshal Count Traun, who succeeded Khevenhüller in 1744, thought equally highly of Daun, and entrusted him with the rearguard of the Austrian army when it escaped from the French to attack Frederick the Great. He held important commands in the battles of Hohenfriedberg and Soor, and in the same year (1745) was promoted to the rank of Feldzeugmeister (Lieutenant General). After this he served in the Low Countries, and was present at the Battle of Val. He was highly valued by Maria Theresa, who made him commandant of Vienna and a Knight of the Golden Fleece, and in 1754 he was elevated to the rank of Feldmarschall (Field-Marshal).
Seven Years' War
During the interval of peace that preceded the Seven Years' War he was engaged in carrying out an elaborate scheme for the reorganization of the Austrian army, and it was chiefly through his efforts that the Theresian Military Academy was established at Wiener-Neustadt in 1751. When a Third Silesian War broke out, he was not actively employed in the first campaigns of the war, but in 1757 he was placed at the head of the army which was raised to relieve Prague. On 18 June 1757 Daun decisively defeated Frederick for the first time in his career in the desperately fought Battle of Kolin. In commemoration of this brilliant exploit, the queen immediately instituted a military order bearing her name, and Daun was awarded the first Grand Cross of that order. The union of the relieving army with the forces of Prince Charles at Prague reduced Daun to the position of second in command, and in that capacity he took part in the pursuit of the Prussians and the victory of Breslau.