The empire of Louis the Pious, son of Charlemagne, had originally split in three parts by the 843 Treaty of Verdun: Lothair I, his eldest son, received the Imperial crown and the personal realm of Middle Francia Louis the German, the second born son, received East Francia Charles the Bald, his half-brother, received West Francia, although this was disputed by Pepin II of Aquitaine until he was captured
Division of 855
Upon the death of Lothair I in 855, his realm of Middle Francia was partitioned between his sons by the Treaty of Prüm: Louis II of Italy, the eldest son, received the imperial crown and Italy Charles of Provence became King of Provence, later partitioned by Louis II and Lothair II Lothair II received Austrasia, Frisia and Upper Burgundy – this realm came to be named Lotharii Regnum East Francia and West Francia remained as before: Louis the German ruled East Francia Charles the Bald ruled West Francia Lothair II ceded the southeastern parts of Upper Burgundy to his brothers, whereas Charles of Provence received the bishoprics of Belley and Tarentaise in 859, and Louis II of Italy the bishoprics of Geneva, Lausanne and Sion a year later.
Division of 863
suffered from epilepsy and died heirless in 863, and his kingdom was partitioned between his brothers. Lothair II, his heir, received only the western Lower Burgundian parts which were bordering his western Upper Burgundy, while Louis II received the whole rest of the Kingdom of Provence.
Treaty of Meerssen
In 869 Lothair II died without legitimate children so his heir was his brother, Emperor Louis II of Italy. As Louis was at that time campaigning against the Emirate of Bari, his uncles, Louis the German and Charles the Bald, took his inheritance. Charles had himself crowned in Metz the same year, but was forced by his brother to partition the short-lived Lotharingia, together with the lands Lothair II acquired after the death of Charles of Provence, as they had agreed at Metz in 868. Their contract of 870 at Meerssen replaced the 843 Treaty of Verdun, after which the Carolingian Empire was also split into three parts, by dividing the northern half of Middle Francia stretching from the Rhone valley to the North Sea, in effect recombining sundered territories of Francia into two larger east and west divisions. However, at this time large parts of the Frisian coast were under Viking control and therefore only divided on paper. The borderline ran roughly along the rivers Meuse, Ourthe, Moselle, Saone and Rhone. In the north, Louis received most of Lothair's Austrasia, with his eastern part including both Aachen and Metz, and most of Frisia. But in the south, while Louis received most of Upper Burgundy that was left to Lothair, Charles received Lothair's inheritance in Lower Burgundy and a small western part of Upper Burgundy – this opened him the way to Italy. Louis joined the newly acquired parts of central Austrasia to the subkingdom of his son Louis the Younger in eastern Austrasia, while the illegitimate son of Lothair II, Hugh, was granted the Duchy of Alsace.
Legacy
The arrangement did not endure more than ten years. Upon the death of Louis the German in 876, Charles the Bald, by then King of Italy and Emperor, attacked eastern Lotharingia, but was defeated by Louis the Younger in the Battle of Andernach. In turn, after Charles the Bald had died and his successors struggled to consolidate their rule over West Francia, Louis the Younger campaigned in western Lotharingia in 879. Charles's grandsons were forced to cede the whole Lotharingia to him, sealed by the 880 Treaty of Ribemont, according to which it finally became part of East Francia.
