The First Messenian War, a war between Messenia and Sparta, begins in 743 BCE and ends in 724 BCE, according to the dates given by Pausanias.The war continues the rivalry between the Achaeans and the Dorians that had been initiated by the Return of the Heracleidae (Dorian Invasion).

Both sides utilize an explosive incident to settle the rivalry by full-scale war.

The war is prolonged into 20 years.

The result is a Spartan victory.

Messenia is depopulated by emigration of the Achaeans to other states.

Those who do not emigrate are reduced socially to helots, or serfs.

Their descendants will be held in hereditary subjection for centuries until the Spartan state finally needs them for defense.