After the Persian invasion was turned back Athens formed the Delian League to continue, while Sparta withdrew to deal with its restive serfs at home. Athens progressively exploited and opressed the League and after the Persians agreed to peace, openly turned it into an empire.
They turned the alliance of cities against the Persian Empire into an empire of their own and used the financial contributions of the cities to beautify Athens and keep half its population on the public payroll.
The Assyrian, Babylonian and Hellenic.
The Persian Empire .
Some of the Greek city-stated joined the Persians. The southern Greek states united against the Persians. Doing so stopped them being absorbed into the Persian Empire. For the Athenians, after the initial Persian invasion was repelled, they took over leadership from the Spartans, who were facing internal revolt by their serf population, and when the ongoing Persian Empire attempts were repelled, the Athenians converted the anti-Persian league, which it led, into an empire of its own - half the Greek city-states were effectively subjected to and ripped off by Athens.
It was the site of a battle between Athens and Plataea and a Persian expeditionary force sent to take over Athens and reinstall an Athenian tyrant to prevent it causing further trouble within the Persian Empire. The Athenians repelled the Persian force at the battle.
It spread from Persia through the Middle East, Egypt and Central Asia.
Control over Mesopotamia and Assyria, then over Asia Minor.
It was a courier system, by roads and by sea for official use.
The Persian Empire and a couple of hundred of the city-states of the Greek world.
Athenians felt great pride in their leadership position after the defeat of the Persians. This pride led to achievements.
The Persian Empire.
The Persian Empire was not a person.