Centuries: 6th century BC - 5th century BC - 4th century BC
Decades: 460s BC 450s BC 440s BC 430s BC 420s BC - 410s BC - 400s BC 390s BC 380s BC 370s BC 360s BC
Years: 420 BC 419 BC 418 BC 417 BC 416 BC - 415 BC - 414 BC 413 BC 412 BC 411 BC 410 BC
- End of the Peace of Nicias
- Begin of the Athenian military expedition to Sicily
- Athenian politician Alcibiades is condemned to death and flees to Sparta
- Melos, refusing the Athenian demand to join the Delian League, is attacked and conquered.The surviving male inhabitants were slain and the women and children enslaved -- an atrocity that shocked the sensibilities of her contemporaries.