What was the name of the historical conflict forming Assassin's Creed Odyssey's backdrop?

The Peloponnesian War forms the historical backdrop of Assassin's Creed Odyssey.

The game is set in ancient Greece during the conflict between Athens and Sparta. Its story begins in 431 BCE, the conventional start date of the war, and allows the player to experience political, military, and personal events across the Greek world. The player character can be Alexios or Kassandra, although Kassandra is the canon protagonist in the wider series chronology.

The real Peloponnesian War lasted from 431 to 404 BCE, with interruptions and shifting alliances. Athens and its allies faced Sparta and the Peloponnesian League. Odyssey uses this historical setting while adding fictional characters, mythology-inspired encounters, and the Assassin's Creed series' Isu mythology.

The conflict is often confused with the earlier Greco-Persian Wars, which involved invasions by the Persian Empire. Those wars influenced Greek history but were not the central war depicted in Odyssey.