GUICHARD, KARL GOTTLIEB (1724-1775), soldier and military writer, known as QUINTUS ICILIUS, was born at Magdeburg in 1724, of a family of French refugees. He was educated for the Church, and at Leiden actually preached a sermon as a candidate for the pastorate. But he abandoned theology for more secular studies, especially that of ancient history, in which his learning attracted the notice of the prince of Orange, who promised him a vacant professorship at Utrecht. On his arrival, however, he found that another scholar had been elected by the local authorities, and he thereupon sought and obtained a commission in the Dutch army. He made the campaigns of 1747-48 in the Low Countries. In the peace which followed, his combined military and classical training turned his thoughts in the direction of ancient military history. His notes on this subject grew into a treatise, and in 1754 he went over to England in order to consult various libraries. In 1757 his _Memoires militaires sur les Grecs et les Romains_ appeared at the Hague, and when Carlyle wrote his _Frederick the Great_ it had reached its fifth edition. Coming back, with English introductions, to the Continent, he sought service with Ferdinand of Brunswick, who sent him on to Frederick the Great, whom he joined in January 1758 at Breslau. The king was very favourably impressed with Guichard and his works, and he remained for nearly 18 months in the royal suite. His Prussian official name of Quintus Icilius was the outcome of a friendly dispute with the king (see Nikolai, _Anekdoten_, vi. 129-145; Carlyle, _Frederick the Great_, viii. 113-114). Frederick in discussing the battle of Pharsalia spoke of a centurion Quintus Caecilius as Q. Icilius. Guichard ventured to correct him, whereupon the king said, "_You_ shall be Quintus Icilius," and as Major Quintus Icilius he was forthwith gazetted to the command of a free battalion. This corps he commanded throughout the later stages of the Seven Years' War, his battalion, as time went on, becoming a regiment of three battalions, and Quintus himself recruited seven more battalions of the same kind of troops. His command was almost always with the king's own army in these campaigns, but for a short time it fought in the western theatre under Prince Henry. When not on the march he was always at the royal headquarters, and it was he who brought about the famous interview between the king and Gellert (see Carlyle, _Frederick the Great_, ix. 109; Gellert, _Briefwechsel mit Demoiselle Lucius_, ed. Ebert, Leipzig, 1823, pp. 629-631) on the subject of national German literature. On 22nd January 1761 Quintus was ordered to sack the castle of Hubertusburg (a task which Major-General Saldern had point-blank refused to undertake, from motives of conscience), and carried out his task, it is said, to his own very considerable profit. The place cannot have been seriously injured, as it was soon afterwards the meeting-place