In ancient times stone fortresses were spread both in Greece and in some regions of Persia.
Hoping to defend themselves the Greeks who lived in cities situated in Asia Minor would surround their cities by strong stone walls. But nevertheless siege engines and briberies made them depend on a Persian king. Manifold tries to free a city caused new Persian intrusions and assaults of rebellious cities.
Those Greek cities that helped rebels also suffered invasions of the Persian king Xerxes, but they survived. Having repulsed this invasion, the Greeks undertook their own march in return. Since then the Asia Minor cities and fortresses being defended by Persian garrisons would often see Greek attacks. Thus the Greeks could defend one and the same city from the Persian army and then the Persians would defend it but this time from the Greek and Macedonian armies.