In the Peloponnesian War the Thebans, embittered by the support which Athens gave to the smaller Boeotian towns, and especially to Plataea, which they vainly attempted to reduce in 431, were firm allies of Sparta, which in turn helped them to besiege Plataea and allowed them to destroy the town after capture (427).
In the Peloponnesian War the Boeotians, embittered by the early conflicts round Plataea, fought zealously against Athens.
Hence it took a prominent part in the Peloponnesian War until the crushing defeat at Idomene (426) crippled its resources.
At the end of the Peloponnesian War Lysander restored the scattered remnants of the old inhabitants to the island, which was used by the Spartans as a base for operations against Athens in the Corinthian War.
In accordance with this scheme Pericles sought to educate the whole community to political wisdom by giving to all an active share in the government, and to train their aesthetic tastes by making accessible the best drama and music. It was most unfortunate that the Peloponnesian War ruined this great project by diverting the large supplies of money which were essential to it, and confronting the remodelled Athenian democracy, before it could dispense with his tutelage, with a series of intricate questions of foreign policy which, in view of its inexperience, it could hardly have been expected to grapple with successfully.
During the early Peloponnesian War Argos remained neutral; after the break-up of the Spartan confederacy consequent upon the peace of Nicias the alliance of this state, with its unimpaired resources and flourishing commerce, was courted on all sides.
In this so-called first Peloponnesian War Sparta herself took but a small share beyond helping to inflict a defeat on the Athenians at Tanagra in 457 B.C. After this battle they concluded a truce, which gave the Athenians an opportunity of taking their revenge on the Boeotians at the battle of Oenophyta, of annexing to their empire Boeotia, Phocis and Locris, and of subjugating Aegina.
Two questions of considerable importance for the full understanding of the Peloponnesian War may be selected for special notice: (I) how far was it a war between two antagonistic theories of government.
To him we may also attribute the 3 obols pay which the soldiers received during the Peloponnesian War in addition to the old-established provision-money.
In the first winter of the Peloponnesian War (431 B.C.) Athens expelled the Aeginetans, and established a cleruchy in their island.