Historically, the Saxons who invaded Britain in the sixth century came from Germany, and Geoffrey of Monmouth according lists Hengist and Horsa as German natives. Though the country was divided by number of Teutonic tribes in the fifth and sixth century, several "dukes" or "emperors" of Germany appear in various Arthurian romances.
Among them are an Emperor of Germany whose daughter, Fenice, is the love of Cliges in Chrétien de Troyes’s Cliges; another Emperor of Germany who joins a tournament at Camelot in the Vulgate Lancelot; and Emperor Henry of Germany, who is named as the father of Arthur’s Sir Laris in Claris et Laris.
An Emperor of the Alemanni figures into the tale of Meriadoc. Duke Frollo, who rules Gaul in Geoffrey of Monmouth’s chronicle, is the ruler of Germany (owing his allegiance to Rome) in the Vulgate Merlin, and the Germans join Frollo, Emperor Lucius, and King Claudas in a series of aggressions against Arthur. Frollo had stolen the dukedom from a Duke Mathem.
Germany, Emperor of
In Chrétien's Cligés, this potentate betrothed his daughter Fenice to the Duke of Saxony, but jumped at the chance to break this engagement and give her to Emperor Alis of Greece and Constantinople instead.
This caused plenty of fighting, which might have been seen a further political shrewdness in an age when knights often enough hacked away at one another for far less reason.