A reason is that some people wanted land, so people fought over land.
The loyalty to the city-states was greater than the loyalty to any larger conception of Greece. As a result, city-states would only fight or mobilize in cases where the individual city-state was jeopardized, not out of solidarity with other city-states.
anient greece
cuz they wanted power and fame
the ycould not really due to the sea and mountains.
They wanted to punish the persians for attacking Greece
The mountains and hills of Greece isolated the city-states which cut off connection with other city-states and countries
Persia wanted to include mainland Greece in its empire. The southern city-states disagreed and resisted the takeover.
Greece was not a countries - it was a series of city-states and leagues. They fought or took over them all successively.
Greece is covered for some 80% by mountains that were also densely forested in ancient times. Communities were effectively separated from each other and often had to fight each other over scarce arable land in order to grow enough food to feed their Community. This lack of easy contact and the fight for resources was the main reason that Greece developed into a number of separate city-States who only joined forces to better beat the crap out of other Greek city-States; and only very rarely, to beat an outside enemy like the Persians.
Athens was one of the 2,000 city-states which fought each other over a thousand years.
yes
The citiy-states attacked each other in varying alliances.