We have now reached the outbreak of the Peloponnesian war, where we saw the hostilities between Thebes and Plataea marking a point where the war would begin. Both of these city states were allied to Sparta, in Thebes case and Athens on the Plataean side. Even though preparations for war were underway already, this action would see that both Sparta and Athens would be ready for conflict since this was a blatant breach of the 30 years peace.
However, before moving forward with developments, we are going to take a step back to see if we can get a better understanding of why this war would come to develop. We will first look at what Thucydides our main source says about the causes and his opinions. Remember, here it was his aim in presenting his work to make sure that all those that read it would have an understanding of the events and motivations behind this greatest of Greek conflicts.
We will also explore the notion of the remote causes of the war and more immediate cause. This will see us looking back to even before the Persian War at the interactions between Athens and Sparta, while then following their interactions from the evolving developments of the Persian invasion and their victory in that war. Then we will turn to the years just before the breakout of the Peloponnesian War to see how both Athens and Sparta would come to be involved in this situation that had begun as a regional dispute out of their areas of influence.
Trying to shed light on the causes for war developing in this conflict is not easy task. If we are expecting to find a single cause for the war, we will walk away disappointed. Although, Thucydides would provide what appears on the surface a straight forward answer, when you stop and think about it, there are so many elements tied up in his answer and it becomes apparent why he devoted his entire work to the subject of the Peloponnesian War.