Why did the Peloponnesian War start?

Athens attacked the city-state of Sparta.

The Spartan King stole the Athenian Queen.

The Corinthian King insulted the Athenian King.

Sparta and Corinth became jealous of the wealth and power of Athens

, particularly its growing empire and its control over the Delian League. This led to tensions between the city-states, ultimately resulting in the outbreak of the Peloponnesian War in 431 BC. The war would last for more than 20 years and would have a significant impact on the Greek world.