In 1794 the Left Bank of the Rhine, including the Palatinate, was occupied by French revolutionary troops. As a result of the Treaty of Campo Formio (1797), the First French Republic annexed the region. In 1798 they introduced a new administrative system with the establishment of departments. Basically, the area of the Palatinate became the Département of Mont Tonnerre, laying the cornerstone of its regional identity today. Minor parts of today's region belonged to the neighbouring departments of Sarre and Bas-Rhin. The French further subdivided the department into cantons, mayoralties and municipalities, and introduced their legal system (Napoleonic Code) and the metric system.