The Battle of Deres was a fight between the Spartans

Sparta

Sparta or Lacedaemon, was a prominent city-state in ancient Greece, situated on the banks of the River Eurotas in Laconia, in south-eastern Peloponnese. It emerged as a political entity around the 10th century BC, when the invading Dorians subjugated the local, non-Dorian population. From c...

 and the Messenians, which occurred c. 640 BC, it was the first major military engagement of the Second Messenian War

Second Messenian War

The Second Messenian War was a war between the Ancient Greek states of Messenia and Sparta. It started around 40 years after the end of the First Messenian War with the uprising of a slave rebellion. This war lasted from 685 to 668.-Prelude:...

. The Spartans

Sparta

Sparta or Lacedaemon, was a prominent city-state in ancient Greece, situated on the banks of the River Eurotas in Laconia, in south-eastern Peloponnese. It emerged as a political entity around the 10th century BC, when the invading Dorians subjugated the local, non-Dorian population. From c...

 and Messenians didn't have any allies at the time of conflict and the outcome of the battle was highly disputed. After the battle, the Messenians offered Aristomenes

Aristomenes

Aristomenes was a king of Messenia, celebrated for his struggle with the Spartans in the Messenian Wars , and his resistance to them on Mount Ida for 11 years...

 the crown of Messenia. Aristomenes

Aristomenes

Aristomenes was a king of Messenia, celebrated for his struggle with the Spartans in the Messenian Wars , and his resistance to them on Mount Ida for 11 years...

declined the offer, preferring instead to become general with absolute powers.