DAUN (DHAUN), LEOPOLD JOSEF, COUNT VON ( 17°5-1766), prince of Thiano, Austrian field marshal, was born at Vienna on Sept. 24,17°5. He served in Sicily (1718), in Italy and on the Rhine in the War of the Polish Succession (1734-35), against the Turks (1737-39), and in the War of the Austrian Succession (1740-42). He was present at Chotusitz and Prague, and led the advanced guard of Khevenhiiller's army in the vic torious Danube campaign of 1743. Field MQ.rshal Traun, who succeeded Khevenhiiller 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. After this he served in the Low Countries, and was present at the battle of Val. Maria Theresa made him com mandant of Vienna and a knight of the Golden Fleece, and in 1754 he was elevated to the rank of field marshal.
During the interval of peace that preceded the Seven Years' War he began the reorganization of the Austrian army. He was not actively employed in the first campaigns of the war, but in 1757 he commanded the army raised to relieve Prague. On June 18,1757, Daun defeated Frederick for the first time in his career in the desperately fought battle of Kolin (q.v.). The union of the relieving army with the forces of Prince Charles at Prague reduced Daun to the position of second in command, and as such he took part in the pursuit of the Prussians and the victory of Breslau. Frederick now reappeared and won the most brilli ant victory of the age at Leuthen. Daun was not held account able for the disaster, and when Prince Charles resigned his com mand, Daun was appointed in his place. With the campaign of 1758 began the var of manoeuvre in which Daun, if he missed, through over-caution, many opportunities of crushing the Prus sians, at least maintained a steady and cool resistance to the fiery strategy of Frederick. In 1758 Major-General Loudon, acting under Daun's instructions, forced the king to raise the siege of Olmiitz, and later in the same year Daun himself surprised Fred erick at Hochkirch and inflicted a severe defeat upon him (Oct. 141. On Nov. 20-21, 1759, he surrounded the entire corps of General Finck at Maxen, forcing the Prussians to surrender. These successes were counterbalanced in the following year by the defeat of Loudon at Liegnitz, which was attributed to the dilatoriness of Daun, and Daun's own defeat in the great battle of Torgau (q.v.). In this engagement Daun was severely wounded.
He continued to command until the end of the war, and after wards worked with the greatest energy at the reorganization of the imperial forces. In 1762 he had been appointed president of the H o fkriegsrat. He died on Feb. 5,1766.
See Der deutsche Fabius Cunctator, oder Leben u. Thaten S. E. des H. Leopold Reichsgrafen v. Dhaun K.K.F.M. (Frankfort and Leipzig, 1759-6o), and works dealing with the wars of the period.