Final answer:
Justinian I, reigning from 527 to 565, made several contributions to the Byzantine Empire by enforcing religious unity, leading reconquests in the West, and codifying Roman law through the Corpus Juris Civilis. He commissioned outstanding building projects like the Hagia Sophia and managed affairs with the Persian Empire. Despite his successes, financial strains from military expenses would challenge his successors.
Step-by-step explanation:
Justinian I was the Eastern Roman emperor from 527 to 565 and is noted for his significant contributions to both the Byzantine Empire and potentially the Western world. He was a devout Christian and sought to enforce religious uniformity by dealing with heretical sects and imposing Roman law. Justinian realized these goals through various methods, including drafting laws to address religious matters and leading military campaigns for reconquest and against heresies like Arianism.
His reign is especially remembered for the codification of Roman law in the Corpus Juris Civilis, which is the foundation of legal systems in Europe. Another hallmark of his rule was the expansive building projects, notably the construction of the Hagia Sophia, a symbol of Byzantine architectural achievement. Moreover, Justinian ambitiously set out to reestablish the Roman Empire's lost territories, overseeing the reconquest of parts of the western empire and dealing with the threat of the Persian Empire to the east.
Despite these achievements, the expenses incurred from military campaigns and constructions imposed significant strains on the empire's finances. Following Justinian's death, the empire faced difficulties maintaining his conquests and defending against continued Persian aggression.