East Francia (Latin: Francia orientalis) or the Kingdom of the East Franks (regnum Francorum orientalium) was a successor state of Charlemagne's empire and precursor of the Holy Roman Empire. Until 911 it was ruled by Carolingian dynasty. It was created after the 840-43 civil war between Charlemagne's grandchildren which ended with the Treaty of Verdun which divided the former empire into three kingdoms. By the middle of the 10th century, the kingdom had become usually referred to as Kingdom of Germany or the Holy Roman Empire, therefore making it the earliest stage in the development of the modern German state.
The east–west division, enforced by the German-Latin language split, "gradually hardened into the establishment of separate kingdoms", with East Francia becoming the Kingdom of Germany and West Francia the Kingdom of France.
The term orientalis Francia originally referred to Franconia and orientales Franci to its inhabitants, the ethnic Franks living east of the Rhine. The use of the term in a broader sense, to refer to the eastern kingdom, was an innovation of Louis the German's court. Since eastern Francia could be identified with old Austrasia, the Frankish heartland, Louis's choice of terminology hints at his ambitions. Under his grandson, Arnulf, the terminology was largely dropped and the kingdom, when it was referred to by name, was simply Francia.
When it was necessary, as in the Treaty of Bonn (921) with the West Franks, the "eastern" qualified appeared. Henry I refers to himself as rex Francorum orientalium, "king of the East Franks", in the treaty. By the 12th century, the historian Otto of Freising, in using the Carolingian terminology had to explain that the "eastern kingdom of the Franks" (orientale Francorum regnum) was "now called the kingdom of the Germans" (regnum Teutonicorum).
Any firm distinction between the kingdoms of Eastern Francia and Germany is to some extent the product of later retrospection. It is impossible to base this distinction on primary sources, as Eastern Francia remains in use long after Kingdom of Germany comes into use. The 12th century imperial historian Otto von Freising reported that the election of Henry the Fowler was regarded as marking the beginning of the kingdom, though Otto himself disagreed with this. Thus:
From this point some reckon a kingdom of the Germans as supplanting that of the Franks. Hence, they say that Pope Leo in the decrees of the popes, called Henry's son Otto the first king of the Germans. For that Henry of whom we are speaking refused, it is said, the honor offered by the supreme pontiff. But it seems to me that the kingdom of the Germans — which today, as we see, has possession of Rome - is a part of the kingdom of the Franks. For, as is perfectly clear in what precedes, at the time of Charles the boundaries of the kingdom of the Franks included the whole of Gaul and all Germany, from the Rhine to Illyricum. When the realm was divided between his son's sons, one part was called eastern, the other western, yet both together were called the Kingdom of the Franks. So then in the eastern part, which is called the Kingdom of the Germans, Henry was the first of the race of Saxons to succeed to the throne when the line of Charles failed ... [western Franks discussed] ... Henry's son Otto, because he restored to the German East Franks the empire which had been usurped by the Lombards, is called the first king of the Germans —- not, perhaps, because he was the first king to reign among the Germans.
It is here and elsewhere that Otto distinguishes the first German king (Henry I) and the first German king to hold imperial power (Otto I).