In 842, Louis the German, son of Louis the Pious, and ruler of the eastern Frankish kingdom, met with his brother, Charles the Bald, ruler of the western Frankish kingdom, at Strasbourg. At this meeting, Louis and Charles pledged their allegiance to each other - and their opposition to the Emperor, their elder brother Lothar.

According to our chief source for the meeting, Nithard's Life of Louis the Pious, each king swore the oath in the vernacular of the other's kingdom. Historians have long used this passage to illustrate the theory that, by 842, Carolingian society had begun to split into separate proto-countries with different languages and customs. Philologists are more interested in the texts of the oaths themselves; in a version of Old French, they are one of the first texts we have written in a Romance language clearly distinct from Latin.

In recent years, however, another theory has come to the fore: the Frankish Kingdom comprised several regna (loosely translated as kingdoms) that had always maintained different customs and dialects. In support of this theory is the fact that both Charlemagne and Louis the Pious sent their sons to be raised in the regna they were meant to inherit as their primary territory, in order to guarantee the support of the people by being familiar with them and their customs.

The text

Old French: Pro Deo amur et pro christian poblo et nostro commun salvament, d'ist di en avant, in quant Deus savir et podir me dunat, si salvarai eo cist meon fradre Karlo, et in aiudha et in cadhuna cosa, si cum om per dreit son fradra salvar dift, in o quid il mi altresi fazet, et ab Ludher nul plaid numquam prindrai qui meon vol cist meon fradre Karle in damno sit.

Old High German: in godes minna ind in thes christanes folches ind unser bedhero gehaltnissi fon thesemo dage frammordes so fram so mir got geuuizci indi mahd furgibit so haldih thesan minan bruodher soso man mit rehtu sinan bruodher scal in thiu thaz er mig so sama duo indi mit ludheren in nohheiniu thing ne gegango the minan uillon imo ce scadhen uuerdhen

Translation: For the love of God and for the Christian people, and our common salvation, starting today, as God will give me the knowledge and the power, I will defend my brother Charles with my help in everything, as it must be done with one's brother, as long as he will do it for me, and with Lothaire I will never treat with my will against my brother Charles.

Old French: Si Lodhuvigs sagrament que son fradre Karlo jurat conservat, et Karlus meos sendra de suo part non lostanit, si jo returnar non l'int pois, ne jo ne neuls cui eo returnar int pois, in nulla aiudha contra Lodhuuvig nun li iv er.

Old High German: oba karl then eid then er sinemo bruodher ludhuuuige gesuor geleistit indi ludhuuuig min herro then er imo gesuor forbrihchit ob ih inan es iruuenden ne mag noh ih noh thero nohhein then ih es iruuenden mag uuidhar karle imo ce follusti ne uuirdhit

Translation: If Louis holds this treaty that he gave to his brother Charles, and if Charles my lord doesn't hold, if I can't change his mind, nor me nor anyone I can change his mind will help him against Louis.