After his defeat at the hands of Lucius Cornelius Sulla during the First Mithridatic War (89-85 BC), King Mithridates had rebuilt his power and armies.

[5] At the start of the Third Mithridatic War, the Roman consul Marcus Aurelius Cotta took his fleet into the Bosphorus; he made his headquarters at Chalcedon, a major port city in Bithynia.

He also sent urgent messages to Lucius Licinius Lucullus, his fellow consul, who was preparing his army in Asia province, that the Pontic invasion was underway and he needed assistance.

An advance party of Bastarnae managed to break the bronze chain which blocked entrance to the port, and the Pontic fleet sailed in.

[8] With Cotta bereft of an army and fleet, his local support melted away, Nicaea, Lampsacus, Nicomedia and Apameia, all major cities in the region, fell to Mithridates or opened their gates to him.

Only nearby Cyzicus remained in the Roman camp, probably because many of its citizens (serving in Cotta's army as auxiliaries) had died fighting against Mithridates at Chalcedon.

During the siege of Cyzicus, Lucullus was able to establish a counter-siege; Mithridates' army was destroyed by famine and plague, and the king fled back to Pontus.