What was Alexander the Great biggest accomplishment

Alexander the Great's conquests freed the West from the menace of Persian rule and spread Greek civilization and culture into Asia and Egypt. His vast empire stretched east into India.Although king of ancient Macedonia for less than 13 years, Alexander the Great changed the course of history. One of the world's greatest military generals, he created a vast empire that stretched from Macedonia to Egypt and from Greece to part of India. This allowed for Hellenistic culture to become widespread. He then set out to conquer the massive Persian Empire. Against overwhelming odds, he led his army to victories across the Persian territories of Asia Minor, Syria and Egypt without suffering a single defeat. His greatest victory was at the Battle of Gaugamela, in what is now northern Iraq, in 331 BC.

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answer; collective security;