The Battle of the Lycus was fought in 66 BC between an army of Roman Republic under the command of Pompey the great and the forces of Mithridates VI of Pontus.
The Romans won the battle with few losses; their victory turned out to be decisive with Mithridates fleeing to the Kingdom of the Bosporus (north of the Black Sea) and committing suicide a few years later (in 63 BC), finally ending the Third Mithridatic War.
Mithridates withdrew to the centre of his mountainous kingdom, drawing Pompey after him, denying him supplies by burning the crops, and harassing him with his own superior cavalry.
The cavalrymen ran back to the camp to get their horses but this caused a general retreat because their companions did not know why they were running away and they did not want to stay and find out.
After a difficult journey around the eastern half of the Black Sea, Mithridates arrived in the Bosporan Kingdom and made himself its king after murdering his son.