The Peloponnesian war could only have been avoided if each side was willing to make large compromises which would be completely against their personality or culture. Though there was tension between the two states, it ultimately started outside the two city-states in Corcyra. The battle between Corcyra and Corinth was the spark of the Peloponnesian War. Corinth was allied with Sparta. The odds were not good for Corcyra who turns to Athens as an ally.
Now, the decision that next affected the Peloponnesian War was the fact that Athens had to make a military and diplomatic decision in which no one would be satisfied. They risked antagonizing Sparta or losing a large naval resource in Corcyra to the Corinthians who had their eyes on Athens. The compromise to avoid war was for Athens to not ally with Corcyra and let Corinth increase their navy. If that happened, Athens might have been facing her own downfall. To get even, Athens did make one move that could have played a part in preventing war.
Potidaea, being forced by Athens to choose sides, was childish and just pushed Corinth further as they were licking their wounds. Athens did not have to make that move. From this point on, many of Athens decisions were vindictive in nature, such as punishing Megara for their part in the Battle of Sybota and accusing them of illegal activities.
It was Pericles, who was known for his persuasive political manner, who was the one to push Athens to colonizing. By opening up channels for food sources, the city-state could be stronger and not as cut off from needed resources. What he did not take into account was the reaction of those around them and the cultures that he came up against, as in Corinth. It seems that Pericles was determined to grow a stronger Athens that would be prepared for another “Persia”, but did not look ahead to the effects of his decisions. This is evident during the Archidamian War when he tried to bring all the farmers into the city and hold out in a siege. The logistics were not good and resulted in many unnecessary deaths.
Avoidance of the Peloponnesian War could have occurred, but it would have had to have been a miracle. Each side was refusing to give in. Even their last attempt of peace was a mockery as both Sparta and Athens demanded what they knew would not be answered. (6) They were begging for a war. The only true point that war could have been avoided was with Potidaea where Athens made the first move that did not seem all that necessary in the scheme of things.
Sarah B. Pomeroy et al., Ancient Greece: A Political, Social, and Cultural History (New York: Oxford University Press, 2008).