Beginning of an era
Alexander's father was king of macedonia, so when he was assassinated; Alexander was set to be the successor but was only 20. A rebelilion rose against macedonia, but alexander lead the troops to destroy the rebellion.
Alexander was able to take greece easily, after the athenians and spartians weaken greece in the Pelponnesian War. Then move to take the Asia minor and Persia. When he invaded Egypt, he established the most important city, Alexandria.
It was a blend of Greek, India, Egypt, and Persia cultures. Alexander enthralled the ideas to mix cultures he conquers.