The Battle of the Rhyndacus occurred in 73 BC between a Roman Republican force under the command of the proconsul Lucius Licinius Lucullus and a division of the army of Mithridates VI of Pontus as part of the Third Mithridatic War.
Lucullus, based in Cilicia, had foregone his planned invasion of Pontus from the south to come north and rescue his colleague, proconsul Marcus Aurelius Cotta, whom Mithridates had besieged at Cyzicus on the Sea of Marmara.
With the onset of winter and running low on supplies, Mithridates decided to send his sick, his wounded, and his cavalry east into Bithynia.
In the middle of a snowstorm, Lucullus met these forces with ten cohorts along the banks of the Rhyndacus.
The battle was hard, and the Pontic forces fought bravely, but were unable to withstand the pressure of the Roman attack.