Thucydides' History of the Peloponnesian War is an account of the war fought between the Peloponnesian League (Sparta and its allies) and the Delian League (Athens and its allies) from 431–404 BCE.

Thucydides' History of the Peloponnesian War is seen as one of the first great works of western history. He's been particularly praised for his objectivity and attempt at historical analysis, as he spends considerable time exploring the causes of the war. One can contrast Thucydides' chronicling approach with the more meandering and subjective storytelling of Herodotus in the Histories, the other great historical work of this time.

The Peloponnesian War is broken into eight books and is a detailed account of the conflict. The conflict begins when the Spartans attack Attica, the surroundings of Athens, and lay siege to Athens itself. The Athenians respond with naval attacks on Spartan territory.

A plague strikes Athens and forces the Athenians' hands, which leads to an Athenian defeat. As the book continues we witness the ebb and flow of the war and its seasonal nature. Each year, it seems, the Spartans attack Attica and the outskirts of Athens.

The tide of battle truly turns after the Athenians fail in their attempt to take Syracuse, a Greek colony far to the west on the Italian Peninsula. This ill-fated naval expedition and the shifting loyalties of certain individuals (in particular the General Alcibiades, who famously betrays the Athenians) leads to an eventual Spartan victory.

Throughout the text, Thucydides explores all sorts of important details of the war including technology and military tactics. One of the ways he tells the story is through long speeches and orations that he recalls in great detail. Particularly famous in this respect is Pericles's Funeral Oration, a rallying cry to the Athenians as the city is besieged by the Spartans and struck by the plague. In this respect the History of the Peloponnesian War is also one of the first examples of true political history.

Thucydides' classic text remains one of the best known pieces of Greek writing and has been translated and reprinted numerous times.