Why Ancient Greek City-States Fought Each Other

Ancient Greece was a constellation of independent poleis (city-states) — Athens, Sparta, Corinth, Thebes, etc. — that frequently warred. Core causes:

1. Resource Competition: Scarce arable land, water, silver, timber drove territorial disputes.
2. Political Rivalry: Democracy (Athens) vs. Oligarchy/Spartan mixed regime; ideological export/defense.
3. Hegemonic Ambition: Stronger states (Athens, Sparta, Thebes, Macedon) sought empire or leadership (hegemonia).
4. Cultural & Religious Differences: Dialects, cults, festivals; Panhellenic sanctuaries (Olympia, Delphi) were arenas for both unity and competition.
5. Personal & Dynastic Feuds: Elite families (Alcmaeonids, Agiads) pursued vendettas across generations.
6. External Manipulation: Persia funded proxies; later Macedon exploited divisions.

The Peloponnesian War (431–404 BCE) epitomizes this: Athens' naval empire vs. Sparta's land league, devastating both. Unity only came under Macedonian force (Philip II, Alexander).