At that time there was feudalism, where people answered to their feudal lords. These lords would fight each other for power and territory.
The battle of Ephesus was in Asia Minor in 498 BCE involving the Persians and the Ionian Greek cities supported by Eretria and Athens from mainland Greece. The Persians won.
A combined southern Greece fleet led by Sparts against a Persian fleet drawn from Phoenician, Asian Greek cities and Egypt.
To block the land advance of the Persians at the Thermopylai pass, and so force a naval battle in an attempt to defeat the threat of the Persian fleet to the cities of southern Greece. The naval battle failed, but a later one at Salamis succeeded, enabling the cities to change their posture from each defending itself to concentrating against the Persian army.
to be honest there are 6 city states in greece
Athenian soldiers,sent to assist the Greek cities in the Ionian Revolt against Persia, over-reached themselves by burning the temples and gods in the Persian provincial capital of Sardis.
Three cities that are in and border Greece are Thesoloniki, Larissa, and Patras
Athens is one of the city in greece
look ref: greece
By obstructing the pass, the Persian army's advance into southern Greece was delayed. As the Persian fleet threatened the Greek cities and the cities kept their armies at home guarding against an amphibious attack on them, the Greeks plan was to provoke a sea battle to destroy the Persian fleet. The idea was that holding the pass would force the Persians to try to outflank the position by sea, and the Greek fleet would pounce. Unfortunately for the Greeks the sea battle went against them, so holding the pass was to no avail. The troops holding the pass were therefore withdrawn. The Spartan contingent selflessly continued to hold to let the other city contingents escape.
The Persian Empire had expanded during the 6th Century BCE to absorb the Middle East, and in the process had taken control of the numerous Greek cities dotted around the coast of Asia Minor. Some of the cities of mainland Greece continued to support the cities, which they had colonised in Asia, in revolting against Persian rule, culminating in a failed uprising in the early 5th Century BCE known as the Ionian revolt. After failed further revolts, Persia sent a punitive expedition against the cities of the island of Euboia and Athens (who were Ionian Greek) with the intention of installing puppet regimes. This was defeated at the battle of Marathon in 490 BCE. Persia then decided that the only way to put an end to this was to establish an ethnic frontier by absorbing the Greek states in mainland Greece. They began with the cities around the northern Aegean Sea and islands. Then they began to subvert the cities of central Greece with bribes. Finally they invaded with an army comprised of the best contingents from their empire, and a war fleet raised from Phoenecia, Egypt and the Asian-Greek cities. They were opposed by the cities of the Peloponnese Peninsula, Athens, Phokia, Euboia and other smaller states and islands.
Serres is a city in Greece
They turned the Delian League which they led against the Persians into an empire, and levied an tax on the cities, collected annually by a fleet of 100 warships. The cities regarded it as stealing.