The war party within Sparta now had the majority in favour of their policy towards Athens. A clear vote had seen that the policies of the peace that had influenced much of Spartan policy since the end of the Persian invasions had now fallen out of favour. This would see that Sparta now saw that Athens had breached the 30 years peace, created nearly 15 years ago. However, for war to be the next step in developments a congress of the Peloponnesian league would need to be held for all its members to vote on the matter.
Sparta would host the congress of the Peloponnesian League to put the matter to all members. It would be important to have everyone on board for a coming struggle with Athens and its empire. Thucydides would highlight that many would speak in favour of war with a particular focus on the speeches delivered by Corinth, where they would convince all that Athens could be defeated.
The Congress would decide that war would be the best path forward, as Athens needed to be stopped. However, conflict would not develop just yet, with Sparta sending a number of embassies to deliver ultimatums to Athens. These were supposedly an attempt to avoid war, but the conditions were demands that Athens could not accept and no arbitration was attempted. Finally, with Athens rejection, diplomatic connections would officially break down.
Conflict between the two would still not develop, though up in Boeotia an action by Thebes, Sparta’s ally, would see the first action leading to the outbreak of the Peloponnesian War. They would target the small polis of Plataea, an ally of Athens, though with the action not going as Thebes planned, more conflict was sure to follow. What took place in Boeotia would be a clear breakdown of the 30 years peace, with Athens and Sparta now on a war footing.