West and East Francia drift apart linguistically

Charlemagne’s multi-ethnic empire was also linguistically diverse, with two major language groups –the Latinesque Gallo-Roman and a variety of Germanic dialects – competing with a number of minor tongues.

The death of Charlemagne’s successor, Louis the Pious, in 840 sparked a war of succession. Charles the Bald and Louis the German allied against their elder brother the Emperor Lothar. The oaths ceremony held on 14 February 842 to seal this alliance highlighted the linguistic diversity of the empire. Whilst the principle allies spoke their lines in Old French, Old High German and Rhine Franconian, their lieutenants each gave their oaths in their own language.

Despite their inability to agree on a single language, the two leaders were militarily successful. Charles and Louis both carved out a kingdom separate from Lothar – Charles in the West and Louis in the East. Lothar’s central kingdom was divided up between West and East Francia shortly after his death in 855 and the two kingdoms continued on their separate ways, eventually providing the starting point for present-day France and Germany.