For the 50 years of the War 499-449 BCE, most of the normal fighting between Greek city-states was diverted to opposing Persian attempts to bring peace to the Eastern Mediterranean.
At the end of the War, Persia gave up and the city-states went back to their normal fighting between each other.
There was little Greek unity. The Greek world comprised several hundred independent city-states some of which from time to time joined several leagues, and even changed leagues as it suited them.
So there was no Greek unity. After some of the states joined together to repel the Persians, they then returned to fighting each other. Again, leagues appeared and dissolved.
Their unifying factor was quasi-religious - the Amphytionic League whic pontificated on religious and cultural matters, however this was eventually harnessed by proxies of Phillip II of Macedonia, a nom-member - as a control measure in Greek affairs.
It did not lead to Greek unification. Half the Greek states were on the side of Persia, and after the southern Greek city-states repelled the persian invasion, they went back to their usual activity to fighting each other, leading eventually to the disastrous Peloponnesian War which devastated Greece.
With the threat of takeover by Persia, the city-states united to repell it as none were capable of resisting by themselves. After peace was made when the invasion was repelled, the Greek city-states went back to fighting each other.
The Greek polis in mid and northern Greece were unified in joining Persia's attack in the southern Greek polis which unified in defeating the Persian force and its Greek polis allies.
For survival as independent city-states.
Persian Wars.
The Persian-Greek wars stretched from 499-449 BCE in several phases. There were not two distinct wars.
The Greek city-states were able to return to their usual wars amongst each other, and a series of wars so devastated them that they became an easy mark for a Macedonian takeover.
The Persian army, and the armies of the Greek city-states.
The Greek city-states were freed to go back to their endles wars amongst each other, with horrendous effect on the populace.
The Persian king, and first Sparta then Athens on the Greek side.
The Persian Empire and various combinations of Greek city-states.
Persia and Greek city-states.
449 BCE.
Herodotus
Persian wars.
persian wars.