How did ancient Greeks develop an affective way to fight wars?

Answer 1

The independent city-states which made up the Greek world initially fought neighbouring sity-states over land and other disputes. They then began to ally with other city-states fwhere there was a common cause, and this progressively expanded to forming leagues of several, and eventually many city-states. These combined forces became increasingly powerful as they grew larger and branched out to also having large combined fleets of warships.

This was temporarily diverted by the Persian invasion, where some Greek city-states sided with the Persians and some united to oppose the Persian-Greek forces. After the Persian War, the city-states went back to fighting each other, with two powerful Greek leagues led by Athens and Sparta.which fought t devastating 27-year war. After that war, others followed with changing alliances of cities, until Macedonia moved in and established control.

The Greek city-states developed their war fighting by a willingness to settle differences by wars, constant practice, and adapting alliances to make their side more effective.