…will be retrospectively recognized by Sparta as…

Athens enters into an alliance with King Sitalces of Odrysian Thrace in 431 BCE after Nymphodorus, an Athenian, marries Sitalces’ sister.

Nymphodorus then negotiates an agreement between Athens and Perdiccas, where Perdiccas regains Therma.

As a result of this, Athens withdraws her support for Philip, and the Thracians promise to assist Perdiccas in capturing him.

In return, Perdiccas marches on the Chalcidians, the people he had originally persuaded to revolt.

The Boeotian League has meanwhile grown into a close-knit confederacy by 431, organized in eleven districts.

Each district, comprising one or more cities, sends a general (boeotarch), several judges, and sixty counselors to a federal government; the federal council of 660 is probably divided into four panels, each in turn convening for one year.

The vote is given only to the propertied classes.

Thebes, where the council meets, dominates the league since it controls four districts and supplies the best contingent to the federal army.

The other Spartan ally seeking to involve Sparta in a private feud with an enemy is Thebes, …

…whose attack on its neighbor Plataea (an Athenian ally) in time of peace …

Thucydides, not yet thirty years old upon the outbreak of hostilities with Sparta, immediately begins writing his History of the Peloponnesian War.

Convinced that the war will be of epochal significance, he believes that his account will retain permanent value because great wars are bound to occur in future epochs “so long as human nature remained the same.”

Pericles employs a strategy designed to avoid pitched land battles and rely instead on the Athenian fleet's control of the sea to assure Athenian food supplies and secure the empire on whose resources the expensive naval policy depends.

He encourages Athenians to crowd into the city behind the Long Walls, abandoning the Attican countryside to invasion by Sparta's superior army, with whom Pericles means to decline battle. (The Athenians do, however, mount cavalry raids to harass the dispersed foot soldiers of the enemy and to keep up city morale.)

Expenditure on building has been counterbalanced by annual savings from the tribute, and enough capital has been reserved, he thinks, for a long war.

Athens moves its flocks from Attica across to …

…Euboea, whose economic importance is thus raised further still.

Athens devotes naval activity in 431 BCE to stripping Corinth of assets in the northwest—of Sollium, Astacus, and …

…Cephallenia, yet …