Final answer:
The Byzantine Empire survived mainly because of its trained bureaucracy and an experienced and loyal army.
Step-by-step explanation:
The Byzantine (eastern Roman) Empire was able to survive mainly because of its trained bureaucracy and an experienced and loyal army. Unlike the Western Roman Empire, the Byzantine Empire had a well-organized and efficient administration system that allowed it to govern its vast territories effectively. Additionally, the empire maintained a strong military force that successfully defended its borders and repelled invasions.