Research Notes:

Thegan's Vita Hludowici Imperatoris names (in order) "Hlutharius, Pippinus, Hludowicus" sons of Emperor Louis I & his wife Ermengard. His father sent him to govern Bavaria in [Aug] 814.

He was crowned joint Emperor LOTHAIRE I in Jul 817 at Aachen, ruling jointly with his father. He was sent to Italy in 822, where he established his court at Pavia and was crowned King of Italy by the Archbishop of Milan. The Annales Xantenses record that "Ludewicus imperator" gave "filio suo Lothario regnum Langobardorum" in 822. Einhard's Annales record that the emperor sent "Walahum monachum propinquum suum [imperatoris] fratrem…Adalhardi abbatis" to Italy in 822 with "Hlotharius…filium suum".

He was again crowned Emperor, at Rome 5 Apr 823 by Pope Pascal I. The rivalry with his father and brothers was exacerbated by the unexpected birth of his half-brother Charles in 823. Tension was increased when Emperor Louis invested Charles with Alemannia, Rhetia, Alsace and part of Burgundy at Worms in Aug 829, reducing Lothaire's territory to Italy. Lothaire and his brothers rebelled in Mar 830, captured their father at Compiègne, and forced him to revert to the constitutional arrangements decided in 817. However, Emperor Louis reasserted his authority at the assemblies of Nijmegen in Oct 830 and Aix-la-Chapelle in Feb 831, and deprived Lothaire of the imperial title and relegated him once more to Italy. A further revolt of the brothers followed. Emperor Louis was defeated and deposed by his sons at Compiègne 1 Oct 833. He was exiled to the monastery of Saint-Médard de Soissons. Lothaire declared himself sole emperor 30 Jun 833, but was forced to flee to Vienne by his brothers Pepin and Louis, who freed their father. Emperor Louis was restored 1 Mar 834, crowned once more at Metz 28 Feb 835. Lothaire captured Chalon-sur-Saône, but was arrested by his father's troops near Chouzy. His father pardoned him and sent him back to Italy as king. Emperor Louis proposed yet another partition in favour of his son Charles at the assembly of Aachen in 837, which was implemented at the assembly of Worms 28 May 839 when he installed his sons Lothaire and Charles jointly, the former taking all land east of the River Meuse, the latter everything to the west, and set aside the claims of his son Louis and the successors of his late son Pepin. Lothaire succeeded as sole emperor on his father’s death 20 Jun 840. He sought to extend his power base northwards from Italy across the Alps, and deprive his half-brother Charles. The latter allied himself with his half-brother Louis, and together they defeated Lothaire at Fontenoy-en-Puisaye, near Auxerre 25 Jun 841. After retreating to Aachen, Lothaire was forced out to Lyon in Apr 842 by his brothers, who declared him incapable of governing the empire. Preliminary peace proposals signed on an island in the Saône, near Mâcon 15 Jun 842 led to the Treaty of Verdun 11 Aug 843, under which the territory of the empire was divided between the three brothers. Lothaire retained the imperial title and was also installed as LOTHAIRE I King of Lotharingia, a newly created territory covering a wide strip of land from the North Sea coast southwards to Italy, the new country being named after him. He established his seat of government at Aachen, and installed his son Louis as King of Italy. Over the following ten years, a series of meetings aimed to maintain peace between the three brothers, with varying success. After a serious illness, Emperor Lothaire abdicated in Sep 855 at Kloster Schüller, near Prüm, and divided his territories between his sons Louis II, Lothaire II and Charles.

The Annales Bertiniani record that Emperor Lothaire entered "monasterium Proneæ in Arduenna", was tonsured, died "IV Kal Oct" and was buried in the monastery. The necrology of Prüm records the death "855 III Kal Oct" of "Lotharius imperator". ¹