What were the major factors that provoked the Peloponnesian War?

Answer 1

Athens led the anti-Persian league of a couple of hundred Greek city-states - the Delian League - levying financial contributions to maintain the fleet it provided as its core. After peace was arranged with the Persian Empire, Athens continued the levy, by force if necessary, and spent the money on itself, creating an empire of its own. It used its power and money to interfere in the affairs of Greek cites outside its empire, and so came into collision with the Peloponnesian League led by Sparta.

This war spread well beyond mainland Greece to Asia Minor in the east and Sicily in the west, which stopped an early resolution as Sparta had expected. It came to an end when Persia got back at Athens by financing a Peloponnesian fleet to match Athens' fleet, which was defeated, and Athens, isolated and starving had to surrender. Athens was stripped of it's empire and thereafter became a second rate power.

Answer 2

The desire for peace by the Peloponnesians, and in particular Sparta.

The obduracy and over-confidence of Athens which was determined to maintain and expand its influence.

Persia's later financial support to the Peloponnesians which enabled them to fight on and achieve victory.

Answer 3

Athens' successive intervention in Corcyra, Potidaia and Megara involving members of the Peloponnesian League led by Sparta.