1. Financial decline: The Byzantine Empire faced chronic financial difficulties, which affected its ability to maintain a strong military. The empire's revenues declined due to various factors, including the loss of territories, increased spending on civil administration, and the rise of powerful landed aristocracy that competed with the central government for resources.
2. Political instability: The Byzantine Empire experienced periods of political instability, including frequent dynastic changes, civil wars, and power struggles. This instability often diverted resources and attention away from military affairs and weakened the empire's ability to respond effectively to external threats.
3. Territorial losses: The Byzantine Empire gradually lost territories to various enemies, including the Arabs, Seljuk Turks, and Crusaders. These losses reduced the empire's manpower, resources, and strategic depth, making it more vulnerable to attacks.
4. Military reforms: The Byzantine military underwent several reforms over the centuries, but some of these reforms had unintended consequences. For example, the increasing reliance on professional mercenaries instead of citizen-soldiers led to a decline in military discipline and loyalty. Additionally, the adoption of new military tactics and technologies, such as heavy cavalry and gunpowder weapons, required significant investment and training, which further strained the empire's resources.
5. Internal divisions: The Byzantine Empire was plagued by internal divisions, including religious disputes, ethnic tensions, and conflicts between different factions within the aristocracy and the military. These divisions often led to disunity and hampered the empire's ability to effectively organize and deploy its military forces.
As a result of these factors, the Byzantine military gradually declined in strength and effectiveness, making it increasingly difficult for the empire to defend its borders and maintain its territorial integrity.