Despite these cultural commonalities, affiliations between city-states were loose and short-lived. The Delian and Peloponnesian Leagues, for example, were dominated by one strong city-state. Another good example is how conflict with Persia prompted several city-states to unify against a common enemy, but not all Greek city-states were involved; further, once the external threat was diminished, conflict between the city-states resumed.
Even as Greeks colonized the Mediterranean and Black seas, new colonies, while recognizing a “mother” city-state, were largely independent. Even after Philip II of Macedon brought mainland Greece under his League of Corinth, the individual city-states still retained much of their essential Independent.