Justinian’s attempts at restoring the Roman Empire left the empire at its greatest territorial extent but also consequently in debt, overstretched and vulnerable. Did this contribute to the Romans losing Egypt and Syria a century later?
While Justinian certainly did not do the Empire any favors by outstretching the Empire beyond what it could reasonably control, by overtaxing Egypt and persecuting the Miaphysites that lived there, not to mention the Plague that decimated the empire and its citizens, the real problem was the mutual destruction of the Byzantine and Sassanid Persian Empires in the last of their wars, under Emperors Heraclius and Khusrau II, respectively. Nearly every city between Constantinople and Ctesiphon, the Persian capital, had seen the depredations of war, with the Persians conquering the Levant and Egypt and reaching the gates of Constantinople itself while the Romans in turn went into Persian Mesopotamia and devastated it in return. Both empires were economically and militarily exhausted and though the Byzantine Empire was eventually victorious the victory was fairly hollow, merely weakening both empires to the point that the imminent rise of the Arab state was able to easily overrun both the Persians and the Byzantines alike.