At the start of the war,
Nicomedes IV of Bithynia had lost a battle against two of
Mithridates' most trusted generals (brothers
Neoptolemus and
Archelaus) in the
Battle of the River Amnias. This battle, along with the Battle of Protopachium, would eventually lead to Rome's retreat from Asia Minor. As a result of the first battle,
Manius Aquillius was sent as an ambassador to restore Nicomedes' power. Aquillius found Nicomedes retreating south with Gaius Cassius (the
proconsul of
Asia) and decided to patrol eastern
Bithynia, where Mithridates was likely to go. When Aquillius saw that he was severely outnumbered, he retreated to river
Sakarya, which part of Mithridates' army (under the command of Neoptolemus and Nemanes) eventually caught up with them near the fortress of Protopachium in eastern Bithynia. Nemanes had been sent by
Tigranes the Great, an ally and son-in-law of Mithridates, to take care of the Roman threat by helping Mithridates. == Battle ==