The world in 420 BC — what happened that year

8 events the sources record for this year, grouped by region.

What happened

The Argive army marched against Troezen, a Spartan ally. (Diodorus Siculus, Library of History 12.78.2)
The Mantineans led their whole army, together with the allies, against the Spartan forces. (Diodorus Siculus, Library of History 12.79.4)
He allies Argos, Mantinea and Elis with Athens (Plutarch's Parallel Lives Plut. Alcibiades 15)
Argive envoys obtain in Sparta a 50-year truce proposal under which the Cynuria question can be settled by battle (Thucydides, History of the Peloponnesian War 5.41.2)
When Spartan envoys report the demolition of Panactum and the prisoners, Athens grows angry and sends them away (Thucydides, History of the Peloponnesian War 5.42.2)
Athens concludes a 100-year alliance with Argos, Mantinea and Elis (Thucydides, History of the Peloponnesian War 5.47.1)
At the Olympic festival Elis bars Spartans from the sanctuary and the games for failing to pay a fine (Thucydides, History of the Peloponnesian War 5.49.1)
In Trachinia, neighboring tribes defeat the Heracleans, and the Spartan commander Xenares is killed (Thucydides, History of the Peloponnesian War 5.51.2)