Sokolnicki studied in Warsaw's Corps of Cadets and fought in the Polish-Russian War of 1792 as well as the Kościuszko Uprising of 1794. In 1797 he presented the French Directory with a document entitled "Aperçu sur la Russie". This became known as the so-called "Testament of Peter the Great", which Napoleon Bonaparte used for anti-Russian propaganda purposes in 1812, and has been widely publicised since although scholars have since established that the document is a forgery.