What ancient civilization was united by Alexander the Great to form an empire?

The civilization united by Alexander the Great to form an empire is Persia. Alexander the Great, who was known for his military conquests, primarily expanded his empire by conquering the Persian Empire, which was one of the most powerful civilizations of the time. Although Greece played a significant role in Alexander’s life as he was Macedonian and influenced by Greek culture, the term “empire” in this context most accurately refers to the vast territories he inherited and conquered, which included much of Persia.

While parts of Greece were part of his conquest, the primary focus of his campaigns and unification efforts were against the Persian Empire, which extended across several regions, including parts of Asia Minor, Egypt, and further east into what is now Afghanistan and India. Thus, the correct answer should indicate the empire he united by conquering and assimilating these various regions under his rule. Alexander the Great's legacy is often associated with the spread of Hellenistic culture that arose after his conquests, which further blends Greek influences into the conquered regions, but the unification primarily pertains to the Persian territories.