420s BC 429 BC: Battle of Chalcis—Chalcidians and their allies are defeated by Athens. 429 BC: Battle of Naupactus—Phormio defeats the Peloponnesian fleet. 429 BC: An outbreak of a plague kills over one-third of the population of Athens. 429 BC: King Sitalkes of Thrace invades Macedonia. 428 BC: Mytilene rebels against Athens but is crushed. 428 BC: Sparta attempts to crush a rebellion on Corcyra, but cancels the effort when the Athenians try to intercept them. 428 BC: The Greek colony of Cumae in Italy falls to the Samnites. 427 BC: The leaders of the Mytilenian revolt are executed. 427 BC: Platea surrenders to the Spartans, who execute over 200 prisoners and destroy the city. 427 BC: The Athenians intervene in Sicily to blockade Sparta from the island. 428 BC: The philosopher Plato is born. 426 BC: Demosthenes unsuccessfully besieges the Corinthian colony of Leukas. 426 BC: When Ambracia invades Acarnania, they seek help from the Spartans and Athenians respectively. The Athenians then defeat the Spartans in the Battle of Olpae. 425 BC: Demosthenes captures the port of Pylos in the Peloponnesus. 425 BC: The Athenians invade Sphacteria and defeat the Spartans in the Battle of Pylos. 424 BC: Sicily withdraws from the war and expels every foreign power. Thus, Athens is forced to withdraw from the island. 424 BC: The Athenians try to capture Megara, but are defeated by the Spartans. 424 BC: The Spartan general Brasidas captures Amphipolis, which is a setback for Athens. Thucydides is held responsible for the Athenian failure and is ostracised. This gives him time to start writing his history book. 423 BC: The Athenians propose a cease-fire, which the Spartan general Brasidas ignores. 422 BC: The Spartans defeat the Athenians in the Battle of Amphipolis, where the Athenian Cleon and the Spartan Brasidas are both killed. 421 BC: The Peace of Nicias puts a temporary end to the hostilities between Athens and Sparta. 420 BC: Alcibiades is elected strategos of Athens and begins dominating Athenian politics.
420s bc 429 bc battle of chalcis—chalcidians and their allies are defeated by athens 429 bc battle of naupactus—phormio defeats the peloponnesian fleet 429 bc an outbreak of a plague kills over one-third of the population of athens 429 bc king sitalkes of thrace invades macedonia 428 bc mytilene rebels against athens but is crushed 428 bc sparta attempts to crush a rebellion on corcyra but cancels the effort when the athenians try to intercept them 428 bc the greek colony of cumae in italy falls to the samnites 427 bc the leaders of the mytilenian revolt are executed 427 bc platea surrenders to the spartans who execute over 200 prisoners and destroy the city 427 bc the athenians intervene in sicily to blockade sparta from the island 428 bc the philosopher plato is born 426 bc demosthenes unsuccessfully besieges the corinthian colony of leukas 426 bc when ambracia invades acarnania they seek help from the spartans and athenians respectively the athenians then defeat the spartans in the battle of olpae 425 bc demosthenes captures the port of pylos in the peloponnesus 425 bc the athenians invade sphacteria and defeat the spartans in the battle of pylos 424 bc sicily withdraws from the war and expels every foreign power thus athens is forced to withdraw from the island 424 bc the athenians try to capture megara but are defeated by the spartans 424 bc the spartan general brasidas captures amphipolis which is a setback for athens thucydides is held responsible for the athenian failure and is ostracised this gives him time to start writing his history book 423 bc the athenians propose a cease-fire which the spartan general brasidas ignores 422 bc the spartans defeat the athenians in the battle of amphipolis where the athenian cleon and the spartan brasidas are both killed 421 bc the peace of nicias puts a temporary end to the hostilities between athens and sparta 420 bc alcibiades is elected strategos of athens and begins dominating athenian politics