Pontos News, a Greek site which covers many aspects of Greece, including its ancient history, has this article about the Battle of Manzikert in 1071 AD.
The main part that was interesting to me was this quote here: “The result of the defeat at Manzikert, which is attributed more to the conspiracy and betrayal of the nobles, was that Byzantium lost first the eastern part of Asia Minor and then its interior territories.“
It is important to remember that there was no succession law in the Byzantine Empire. There was no primogeniture so there was chaos or intense competition.
The nobility in this age were getting more powerful after Basil II’s passing in 1025 AD. He was an emperor who had gripped tightly onto power; as soon as he wasn’t there, the nobles and particularly the bureaucracy began taking power away from the Emperor.
The various emperors who came after him tried to have some semblance of authority, but it wasn’t enough.
While the Emperor’s power in this age was still strong within the domain of military affairs, this was not as decisive or as effective. Basil II had a relationship with his soldiers which was hard to replicate.
When Emperor Romanos IV was captured by the Seljuk Turks, the conviving nobles had all the reason to start civil wars and increasing their power base in the chaos. Trebizond and Nicaea began important power players, a harbinger of the increasing amount of power being put into the hands of nobles.
This is the battle where the Empire truly changed into a medieval empire.
Byzantine-Empire.com 