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Justinian served under the Justinian dynasty, also known as the First Justinian dynasty, which ruled the Eastern Roman Empire (Byzantine Empire) from 518 to 602 AD. The dynasty was founded by Emperor Justin I and is best known for the reign of Emperor Justinian I (527-565), who achieved significant military victories, implemented important legal reforms, and undertook ambitious building projects, including the construction of the Hagia Sophia in Constantinople.