Causes of the war:
According to Thucydides, the cause of the war was the "fear of the growth of the power of Athens" throughout the middle of the 5th century BC. After a coalition of Greek states thwarted an attempted invasion of the Greek peninsula by the Persian empire, several of those states formed the Delian league in 478 BC in order to create and fund a standing navy which could be used against the Persians in areas under their control. Athens, the largest member of the league and the major Greek naval power, took the leadership of the league and controlled its treasury. Over the following decades, Athens was able to convert the Delian league into an Athenian empire. This increase in Athenian military power allowed it to challenge the Lacedaemonians (commonly known as the Spartans), who, as leaders of the Peloponnesian League, had long been the sole major military power in Greece.
The immediate cause of the war comprised several specific actions of Athens that affected Sparta's allies, notably Corinth. The Athenian navy intervened in a dispute between Corinth and Corcyra, preventing Corinth from invading Corcyra at the Battle of Sybota, and placed Potidaea, a Corinthian colony, under siege. The Athenian Empire also levied economic sanctions against Megara, an ally of Sparta. These sanctions, known as the Megarian decree, were largely ignored by Thucydides, but modern economic historians have noted that forbidding Megara to trade with the prosperous Athenian empire would have been disastrous for the Megarans. The decree was likely a greater catalyst for the war than Thucydides and other ancient authors realized, more so than simple fear of Athenian power.
The "Archidamian War."
Sparta and its allies, with the exception of Corinth, were almost exclusively land based powers, able to summon large land armies, which were...