Why did independent city states develop in ancient Greece?

Answer 1

Different nomadic Greek tribes moving into mainland Greece 3000 years ago, after pillaging the countryside, had little option but to start farming themselves to gain a living. These farming centres also started fortify a hill (acropolis) to act as a refuge against other interlopers. These citadels expanded to become cities to accommodate a growing population and commercial activities, and also developed cultural activities.

Each city had it's land and commerce, was self-sufficient and so wanted to retain it's independence. There was interaction between the cities - commercial, social and religious commonality drove this, but self-interest kept the cities independent, and their perceived individual rights and interests continued to drive both independence and inter-city warfare. The latter brought cities into shifting alliances but not into political union, so they remained separate city-states.

The Greeks were such great breeders that not even plagues, famines and wars could stop the populations of successful cites exploding, and as the farmers' plots of land were small and the soil poor, the surplus populations were periodically sent off to found new cities, and these new cities eventually felt the squeeze and sent out colonies of their own. In this way, Greek cities spread all around the Mediterranean and Black Seas - to southern France, Sicily, Italy, North Africa, Asia Minor, the Islands and southern Russia. The cities which today have 'polis' (city) in their name tell the story (eg Naples - Italian Napoli - comes from Greek Nea Polis = New City).

Answer 2

the Greek peninsula is divided by mountains and inlets that separated people