"We" beat, as Eastern Romans, that little barbarian soon enough after his declaration of war against civilised mankind in 800 AD.
In a muddy little village in the World's backwater, named Aachen or Aix-la-Chapelle, this poor barbarian chieftain proclaimed himself "Emperor of the Romans"
It would have been the equivalent of Colonel Qaddafi of Libya proclaiming himself the President of the Unites States of America.
I guess that the true Romans in Constantinople were tearful with laughter at the time.
Yet, it wasn't really funny. Western Latino-Germanic Christendom had begun to grow demographically, economicaly, militarily, and, hence, politically stronger, and wanter their emancipation from the surviving true Roman Empire of the East, the latter being Greek-speaking and Greek-dominated.
The "war" was declared by Charlemagne in 800 AD. After several defeats by the (by now Greek) Romans, the Latino-Germanic world known to this day as the "West", still managed to annihilate Greek Christianity in 1204, capturing Constantinople during the 4th "Crusade".
Modern Greeks can only carry the weapon of the defeated: HATRED against the "West".