A number of different arguments can be developed as to who was theaggressor. Thucydides believed that the Pelponnesians were theaggressors, claiming that Athens had observed the letter of the law ofthe Thirty Years’ Peace. It can be argued that Athens knew that warwith Sparta was inevitable and that she therefore intervened in anumber of situations but without the aim of provoking a war. Even modern authorities come to very different conclusions:
Chester G. Starr, A History of the Ancient World, Oxford and New York1991 [first published in 1965], 341: “If we carefully assess Athenianpolicy 433-431, it may appear that Pericles deliberately broughtmatters to a head; for he banned Megarian traders from Aegean markets, aided theCorinthian colony of Corcyra in its controversy with Corinth, and forbade the subjectstate of Potidaea to draw its annual magistrates from Corinth, as had been thecustom.”G. E. M. de Sainte-Croix, The Origins of the Peloponnesian War,Oxford 1972, 67: “[W]e can see that Corinth was being quiteextraordinarily aggressive towards Corcyra and must bear virtuallythe whole of the responsibility for the consequences which ensued.”Thucydides also struggled with these incidents as a historian, but notabout who was guilty. He struggled with the question whether thesethree incidents were the direct cause of the outbreak of the war orwhether there was a deeper-seated reason. Here is what he has tosay:To the question why they broke the treaty, I answer by placing first anaccount of their grounds of complaint and points of difference, that noone may ever have to ask the immediate cause which plunged theHellenes [Greeks] into a war of such magnitude. The real causeIconsider to be the one which was formally most kept out of sight: thegrowth of the power of Athens, and the alarm which this inspired inLacedaemon [=Sparta], made war inevitable. Still it is well to give thegrounds alleged by either side which led to the dissolution of the treatyand the breaking out of the war[Thucydides, The Peloponnesian War1.23; this is followed by a detailed analysis of the incidents ofEpidamnus, Megara, Potidea.].Simon Hornblower, A Commentary on Thucydides, volume I: Books 1-III, Oxford 1991, 65: “The explicit formulation of a distinction between profoundand superficial causes is arguably Thucydides’ greatest single contribution to laterhistory-writing.”Strategies of Sparta and Athens:The initial strategies of the two Greek superpowers were fairlystraightforward. Since Sparta could only rely on her hoplite soldiers,she invaded Attica, the polisof Athens, every year as soon as theweather conditions allowed them to do so (as a rule no fighting tookplace in winter). They would invade in the early spring and return toSparta in the fall. The first time this happened Athens broughteveryone who lived in the countryside within the city walls andallowed the Spartans to destroy their crops and lands. With her fleet,
safely protected in Piraeus by the long walls, she brought in food andother supplies from other parts of Greece.