Peloponnesian War between Athens and Sparta (431–404 BCE)

1. Theban attack on Plataea sparks open war

   Apr 4, 431 BCELabels: Thebes, Plataea

   A Theban force attempted a surprise seizure of Plataea, an Athenian ally; the failure and reprisals helped trigger open hostilities between the Athenian-led and Spartan-led alliances.

   • Peloponnesian War
   • Britannica

2. First Spartan invasion of Attica begins

   May 1, 431 BCELabels: Sparta, Archidamus II

   Sparta, under King Archidamus II, led invasions of Attica to pressure Athens into battle; Athens largely avoided land engagement, relying on the Long Walls and naval raids.

   • Britannica
   • Peloponnesian War

3. Plague outbreak devastates Athens

   Jan 1, 430 BCELabels: Athens, Plague

   A major epidemic struck Athens amid wartime crowding, killing civilians and soldiers and weakening Athenian morale and manpower during the early war years.

   • Britannica
   • WHE

4. Pericles dies during the plague

   Jan 1, 429 BCELabels: Pericles, Plague

   Pericles—central to early Athenian strategy—died during the plague, contributing to political volatility and leadership changes in Athens.

   • Britannica
   • Peloponnesian War

5. Mytilenean revolt challenges Athenian empire

   Jan 1, 428 BCELabels: Mytilene, Lesbos

   Mytilene (on Lesbos) revolted from Athenian control (428–427 BCE). Athens suppressed the revolt; the subsequent Mytilenean Debate highlighted tensions over imperial punishment and democratic decision-making.

   • Mytilenean revolt
   • Mytilenean Debate

6. Siege of Plataea ends in Spartan-Theban victory

   Jan 1, 427 BCELabels: Plataea, Sparta

   After a prolonged siege (429–427 BCE), Plataea fell; many defenders were executed and the city was destroyed, removing a key Athenian ally on the Boeotian frontier.

   • Siege of Plataea
   • Britannica

7. Athenian victory at Sphacteria captures Spartans

   Jan 1, 425 BCELabels: Sphacteria, Athens

   At Sphacteria (425 BCE), Athenian forces compelled a Spartan contingent to surrender—an extraordinary shock in Greek warfare—giving Athens valuable prisoners and leverage.

   • Sphacteria
   • Britannica

8. Battle of Amphipolis kills Brasidas and Cleon

   Jan 1, 422 BCELabels: Amphipolis, Brasidas

   Sparta defeated Athens at Amphipolis (422 BCE). Both Brasidas (Sparta) and Cleon (Athens) died, removing prominent hawks and easing the way toward negotiations.

   • Amphipolis
   • Britannica

9. Peace of Nicias signed between Athens and Sparta

   Mar 1, 421 BCELabels: Peace of, Athens

   Athens and Sparta concluded the Peace of Nicias, intended to last 50 years, ending the first major phase of fighting (the Archidamian War), though the broader conflict soon resumed.

   • Peace of Nicias
   • Britannica

10. Spartan victory at Mantinea checks Athenian-aligned coalition

    Jan 1, 418 BCELabels: Mantinea, Sparta

    At Mantinea (418 BCE), Sparta defeated Argos and its allies (including Athens), strengthening Spartan land dominance and destabilizing the tenuous post-421 peace.

    • Mantinea
    • 418 BC

11. Athens crushes Melos after siege

    Jan 1, 416 BCELabels: Melos, Athens

    Athens besieged neutral Melos (416 BCE) and, after its surrender, executed adult males and enslaved women and children—an episode later emblematic of harsh imperial policy (the "Melian Dialogue").

    • Siege of Melos
    • Peloponnesian War

12. Sicilian Expedition sails to attack Syracuse

    Jan 1, 415 BCELabels: Sicilian Expedition, Athens

    Athens launched a massive expedition to Sicily (415 BCE), aiming to subdue Syracuse and gain resources and strategic advantage; it became a decisive turning point against Athens.

    • Sicilian Expedition
    • Britannica

13. Athenian forces begin full siege of Syracuse

    Jan 1, 414 BCELabels: Syracuse, Athens

    In spring 414 BCE, the Athenians shifted into sustained siege operations against Syracuse; Spartan and allied interventions increasingly blunted Athenian advantages.

    • Britannica
    • Sicilian Expedition

14. Athenian defeat at Syracuse destroys the expedition

    Sep 1, 413 BCELabels: Syracuse, Athenian expedition

    In September 413 BCE, Athenian naval and land forces suffered catastrophic defeat at Syracuse; many were killed or enslaved, severely weakening Athens and encouraging wider revolt.

    • Britannica
    • Peloponnesian War

15. Oligarchic coup in Athens installs the Four Hundred

    Jun 9, 411 BCELabels: Four Hundred, Athens

    Amid fiscal and military crisis, an oligarchic faction overthrew Athenian democracy and established the Four Hundred (June 411 BCE), reflecting extreme pressure on the wartime polity.

    • Coup 411
    • Britannica

16. Athenian victory at Cyzicus revives war effort

    Jun 1, 410 BCELabels: Cyzicus, Alcibiades

    At Cyzicus (May/June 410 BCE), Athenian commanders including Alcibiades destroyed a Spartan fleet, temporarily restoring Athenian leverage and access to key routes.

    • Cyzicus
    • 410 BC

17. Athenian win at Arginusae followed by political backlash

    Jan 1, 406 BCELabels: Arginusae, Athens

    Athens won a major naval battle at Arginusae (406 BCE), but a subsequent storm prevented rescues; political controversy contributed to the trial and execution of Athenian generals, harming command stability.

    • Arginusae
    • Peloponnesian War

18. Sparta crushes Athenian fleet at Aegospotami

    Jan 1, 405 BCELabels: Aegospotami, Lysander

    At Aegospotami (405 BCE), Lysander’s Spartan fleet destroyed the main Athenian fleet, cutting Athens off from grain imports and effectively deciding the war.

    • Aegospotami
    • Britannica

19. Athens surrenders; Spartan-backed Thirty installed

    Apr 25, 404 BCELabels: Thirty Tyrants, Athens

    After blockade and starvation, Athens capitulated to Sparta in 404 BCE; the Long Walls were dismantled and a Spartan-supported oligarchy (the Thirty Tyrants) took power.

    • Peloponnesian War
    • Thirty Tyrants