In 1801 Napoleon I Bonaparte defeated the forces of the Holy Roman Empire, and the influence of the French threatened the existence of Charles I's minor principality of Isenburg-Birstein amongst others. Charles travelled to Paris to engage in separate negotiations with Napoleon and guaranteed from him the future of his statelet. Thus when in July Napoleon announced the creation of the Confederation of the Rhine independent of the Empire, Prince Charles I was one of the sixteen founding members. Charles mediatised the counties of Isenburg-Büdingen, Isenburg-Wächtersbach and Isenburg-Meerholz, which were ruled by other members of the House of Isenburg, and created a federative principality.