Louis the pious, who was the son of the great Charlemagne, died in 840. He left his three sons (Lotharius, Charles the Bald and Lewis the German) the great Carolingian Empire, which was founded by Charles Martel.
Lotharius claimed overlordship over his brothers’ kingdoms and supported his nephew Pepin II who wanted the throne of Aquitaine. But the forces of Charles the bald and Lewis the German defeated Lotharius' troops and forced him to negotiate.
Already, all three brothers had established themselves within the empire:Lotharius in Italy, Charles in Aquitaine and Lewis in Bavaria. Then Lotharius received the central portion of the empire (Italy and the territory between the Rhine and the Rhone rivers) which was called the Central Frankish Realm, and he received the imperial title (this did not mean that he did have overlordship over his brothers but it was meant as an honor to him). Charles got the western part of the empire, which is now (for the largest part) modern France, in those days it was called the Western Frankish Realm. Lewis received the eastern portion of the empire, which is now (for the largest part) Germany and was called the Eastern Frankish Realm back then.Aquitaine was given to Pepin II under the authority of Charles the Bald.
Lotharius gave Italy to his eldest son, Louis II in 844. When Lotharius died in 855, he divided his kingdom into three parts: the territory already held by Louis II remained his (louis’), the territory of the former Kingdom of Burgundy was granted to his third son Charles, and the remaining territory was granted to his second son Lothar II, whose realm was named Lotharingia, or more popular, Lorraine.
Lothar II traded parts of his lands to Louis II for support of a divorce from his wife, which caused conflicts with the Pope and his uncles. Charles of Burgundy died in 863, and his Kingdom was inherited by Louis II. Lothar II died in 869 with no legitimate heirs, and his Kingdom was divided between Charles the Bald and Lewis the German in 870. Louis II died in 875, and named Carloman, the eldest son of Lewis the German, his heir. Charles the Bald, had the support of the Pope, and was thereby crowned both King of Italy and Roman Emperor. The year after, Lewis the German died. The Eastern Frankish Realm was divided between Lewis the Younger, Carloman of Bavaria and Charles The fat.
With the death of Charles the Fat the once glorious and prospering Carolingian empire had ended.