Guischard, Or Guisehardt Karl Gottlieb, a German writer, born in Magdeburg in 1724, died in Berlin, May 15, 1775. He studied at Halle, Marburg, and Leyden, with the intention of becoming a clergyman; but changing his mind, he entered the military service of Holland. After a single campaign, in which he served as ensign in an infantry regiment, peace having been restored by the treaty of Aix-la-Chapelle, he devoted himself to research upon military art in ancient times, and published in 1758 at the Hague his Memoires militaircs sur les Grees et les Romains. Frederick the Great summoned the author to Bres-lau, bestowed upon him the name of Quintus Icilius by which he was afterward known, and gave him a major's commission. In this capacity Guischard was called into service in Saxony, where he was charged with extortion. The king nevertheless promoted him to a colonelcy in 1763, and continued to treat him with favor. In 1773 he published at Berlin his Memoires historiques et critiques sur plusicurs points d'art militaire, which he dedicated to Frederick. This work is written with clearness and a thorough knowledge of the subject.