What were causes of the Peloponnesian war?

The Peloponnesian War was fought between the city-states of Athens and Sparta, along with their respective allies, from 431 to 404 BC. Several causes contributed to the outbreak of the war:

1. Competition for power: Athens emerged as a dominant power in the Delian League after the Persian Wars, while Sparta led the Peloponnesian League. Both city-states sought to expand their influence and control over other city-states, leading to increasing tensions and rivalry.

2. Dispute over the control of Corinth: Athens supported Corcyra's rebellion against Corinth, a key Spartan ally. This event escalated into a conflict and led to a naval battle between Athens and Corinth in 433 BC, further straining relations between Athens and Sparta.

3. Megarian Decrees: Athens imposed economic sanctions on Megara, a city-state allied with Sparta. These measures restricted Megarian trade and were seen as a direct threat to Spartan interests, leading to heightened tensions between Athens and Sparta.

4. Fear of Athenian imperialism: As Athens expanded its empire and influence through the Delian League, many city-states, including Sparta, began to fear that Athenian power would gradually erode their autonomy. This fear motivated Sparta to join forces with other anti-Athenian city-states and start the war.

5. Disputed alliances: Various city-states throughout Greece were divided in their allegiances to Athens or Sparta, creating a complex web of alliances that further contributed to the escalation of conflicts.

6. Proxy wars: Athens and Sparta often supported rival factions within other city-states, such as in the case of Athens supporting Argos and Sparta supporting Elis. These proxy wars heightened tensions and led to further conflicts.

7. Divergent political systems and ideologies: Athens was a democracy, known for its encouragement of artistic and intellectual pursuits, while Sparta was an oligarchy, known for its strict military society. The differing political systems and ideologies served to deepen the divide between the two city-states.

These causes, along with the actions and decisions of various Greek city-states and their leaders, ultimately led to the outbreak of the Peloponnesian War.