Final answer:
The Byzantine Empire steadily lost territory due to external threats, invasions, and weak leadership.
Step-by-step explanation:
The Byzantine Empire steadily lost territory due to various factors. One major reason was the empire's continuous exposure to external threats from hostile states and groups. The empire faced invasions from Persians and Arabs in the seventh century, resulting in significant loss of territory. Additionally, ineffective rulers and conflicts over successors weakened the empire's military capability, leading to the loss of control over overseas territories.