How did the Peloponnesian war broke out

Firstly, this war's name came about due to the long series of conflicts between Athens and Sparta which carried on from 431 to 404 BC. The act that officially sparked the war was when soldiers from Thebes, (which was Sparta's ally), attempted to seize control over a certain town called Potidea. Unfortunately, these soldiers were caught by the inhabitants of the town and were executed. After this act was carried out, a messenger from Athens came to try to talk the people of Potidea out of executing the soliders but it was too late ... the war had been sparked.