in 1777. The major ecclesiastical territory in the region was the Bishopric of Speyer. The Imperial city of Landau joined the Alsacien Décapole in 1521 to preserve its status. Nevertheless, it was seized by France after the Thirty Years' War. Other larger regional entities included the Duchy of Zweibrücken and the Prince-Bishopric of Speyer. The Prince-Bishopric held possessions on both sides of the Rhine. For centuries, the Electoral Palatinate and Bavaria maintained dynastic links because both were ruled by members of the Wittelsbach family. French rule 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. Bavarian rule Following the defeat of Napoleon at the Battle of Leipzig in 1813, and the capture of the Left Bank of the Rhine by the Allies in January 1814; from 2 February 1814, the region was initially under the provisional authority of the General Government of the Middle Rhine, but, from 16 June of the same year, it was placed under the administration of the Imperial-Royal ("k.k.") Austrian and Royal Bavarian Joint Land Administration Commission (k. k. östreichischen und k. bairischen gemeinschaftliche Landes-Administrations-Kommission). In the main treaty agreed at the Congress of Vienna in 1815, and dated 9 June 1815, Article 51 stated that (inter alia), on the Left Bank of the Rhine the former French departements of the Sarre and Mont Tonnerre, except where set forth in the same treaty, were to fall "with full sovereignty" and ownership rights within the overlordship of His Majesty the Emperor of Austria (Herrschaft Sr. Maj. des Kaisers von Oesterreich). Initially, however, joint Austro-Bavarian administration was retained. On 14 April 1816 a treaty was signed between Austria and Bavaria, in which the various territorial changes were agreed on. According to Article 2 of the treaty, Emperor Francis I of Austria ceded various regions to King Maximilian I of Bavaria. These included, in addition