Battle of Potidaea
431 BCE.
Shown on the map at 40.194°, 23.328°.
The Battle of Potidaea was fought in 432 BC between Athens and a combined army from Corinth and Potidaea, along with their various allies. Along with the Battle of Sybota, it was one of the catalysts for the Peloponnesian War.
Text from the Wikipedia article Battle of Potidaea, licensed CC BY-SA 4.0.