Lothar I (c. 795 – 855) - Titles: King of Italy (from 818), Co-Emperor (from 817), Emperor and ruler of Middle Francia (840–855).
Lothar I was the hinge of the Carolingian world—the son who inherited Rome and Aachen, fought his brothers for the rest, and then carved out a long, thin realm running from the North Sea to the Tiber. His life explains why medieval Europe fractured the way it did and why the lands between France and Germany have been contested ever since.
A Prince Made for the Empire
Born to Louis the Pious and Ermengarde of Hesbaye, Lothar grew up as the dynasty’s designated center of gravity. In 817 his father issued the Ordinatio Imperii, a constitutional blueprint that made Lothar co-emperor and senior partner in the family firm, while his younger brothers Pippin (Aquitaine) and Louis (Bavaria) ruled as sub-kings. Lothar also received Italy—with Pavia and Rome—giving him the imperial crown’s deepest historical roots.
Family War
The tidy scheme unraveled when a late-born half-brother, Charles the Bald (823), had to be fit into the inheritance. Lothar fought to keep the senior share. In 830 and again in 833 he joined aristocratic coalitions against their father; the notorious “Field of Lies” saw Louis the Pious deposed, only to be restored a year later. The family compact was now poisoned. When Louis died in 840, Lothar tried to claim the whole empire. His brothers Louis the German and Charles the Bald allied against him (sealed by the Strasbourg Oaths of 842) and broke his bid in the grinding battle of Fontenoy (841).
Verdun and the Middle Kingdom
The Treaty of Verdun (843) ended the civil war by dividing Charlemagne’s creation into three. Lothar kept the imperial title and a “middle kingdom”—a vertical strip from Frisia and the lower Meuse through Lorraine and Burgundy to Provence and Italy, with Aachen and Rome as its symbolic poles. The geography was dramatic and fragile: alpine passes bound north to south, but rivers, languages, and local elites pulled east and west.
Ruling from Rome and Aachen
Lothar governed as a traveling emperor. In Italy he confirmed papal privileges and asserted imperial oversight in Lombard law courts; in the north he issued charters, managed coinage, and worked through bishops and abbots to keep order across long corridors of land. Ecclesiastically, he moved within the archiepiscopal orbit of Trier and the broader Frankish church, while imperial status gave him leverage that ordinary kings lacked. Monasteries—wealthy, literate, and networked—were crucial to that governance. Lothar’s patronage of houses like Prüm both extended his authority and tied his name to the sacred landscape.
Abdication at Prüm
By the mid-850s age and illness pressed in. In 855 Lothar abdicated, withdrew to Prüm Abbey in the Eifel, took the monastic habit, and died there soon after. Before retiring he staged a final act of statecraft: the Treaty of Prüm, which partitioned his realm among his three sons—
Louis II received Italy and the imperial title,
Lothar II took the northern lands that would soon be called Lotharingia,
Charles of Provence ruled Provence and Lower Burgundy.
Aftermath and Legacy
Lothar’s death set Europe on the path we recognize. His Middle Francia did not endure as a single unit. After his sons died—Lothar II without legitimate heirs—most of the middle zone was gradually swallowed by the western and eastern kingdoms (see the later Treaty of Meerssen, 870). Yet the idea of the middle lived on: Lorraine (Lotharingia), Burgundy, Provence, and the old imperial axis from Aachen to Rome remained fault lines and meeting places—zones where languages overlapped, bishops mattered, and emperors and kings bargained.
Lothar I was not the conquering colossus his grandfather had been, but he defined the empire’s limits. By fighting and then accepting a share, he turned the Carolingian legacy into a triptych—France to the west, Germany to the east, and a contested middle that has shaped European politics for over a millennium. The monk’s grave at Prüm is the quiet end of a noisy career, and a reminder that the empire’s map was finally redrawn not only by battles and treaties, but also by the institutions—churches and monasteries—that sustained life between them.
Further Reading
Janet L. Nelson, Charles the Bald (for the family politics of Verdun and after)
Rosamond McKitterick, The Frankish Kingdoms under the Carolingians
Timothy Reuter, Germany in the Early Middle Ages
Patrick Geary, The Myth of Nations (on Lotharingia and identity)
Matthias Becher, Karl der Große (background to the imperial idea)
Studies of the Treaties of Verdun (843) and Prüm (855)
Research on Prüm Abbey, Regino of Prüm, and the Carolingian monastic network
