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<br>Justinian ruled the Byzantine Empire during its height. His military faced strength from the East that greatly endangered his people. The Sassanian Empire of Persia was one threat that Byzantines needed to conquer. The Persians endangered eastern lands, so Justinian's military prevented any conquest. The Sassanians were defeated and security was briefly gained. After his success, Justinian wanted to regain lands the Roman Empire once lost to invaders. Byzantine armies began a reconquest of Spain, Italy, and North Africa. Battles against various Germanic groups took place, and western lands were conquered by the Byzantines. The wars were expensive, and resources were low. Defense became weak and territories were lost increasingly after Justinian's death.
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<br>During the early 700s, the Byzantine Empire was in turmoil and chaos. As Leo III took power, Constantinople was being attacked by Avars, Bulgarians, and Arabs. The Arabs from the Middle East were a main concern for Leo III because of their large conquests in the Asia Minor. The Arabs advanced to spread their faith of Islam and control resources. The Arabs slowly acquired land