His realm contained the imperial cities of Aachen (the residence of Charlemagne) and Pavia, but lacked any geographic or cultural cohesion, which prevented it from surviving and forming a nucleus of a larger state, as was the case with West Francia (which became the Kingdom of France) and East Francia (which became the Kingdom of Germany).

Following the 855 partition, 'Middle Francia' became only a geographic term and the bulk of its territory was reorganised as Lotharingia, named after Lothair I's namesake son.

The lands in northern Italy, which extended as far south as Rome and Spoleto, were left to the eldest son Louis II the Younger, crowned co-Emperor in 850 and sole Emperor from 855.

Lothair II received the western Lower Burgundian parts (bishoprics of Lyon, Vienne, Vivarais and Uzès) which were bordering his western Upper Burgundy (remnants of his original Burgundian possessions) which were incorporated into Lotharingia; while Louis II received the Kingdom of Provence.

Louis the German took Upper Burgundy, territory north of the Jura mountains (Bourgogne Transjurane), while the rest went to Charles the Bald.

However, Pope John VIII, dealing with the constant threat of raiders from the Emirate of Sicily, sided with Charles the Bald.