Although the two empires eventually relented and recognized each other's rulers as emperors, they never explicitly recognized the other as "Roman", with the Byzantines referring to the Holy Roman emperor as the 'emperor (or king) of the Franks' and later as the 'king of Germany' and the western sources often describing the Byzantine emperor as the 'emperor of the Greeks' or the 'emperor of Constantinople'. Over the course of the centuries after Charlemagne's coronation, the dispute in regards to the imperial title was one of the most contested issues in Holy Roman–Byzantine politics. Though military action rarely resulted because of it, the dispute significantly soured diplomacy between the two empires. This lack of war was probably mostly on account of the geographical distance between the two empires. On occasion, the imperial title was claimed by neighbors of the Byzantine Empire, such as Bulgaria and Serbia, which often led to military confrontations.
