[2] According to Memnon of Heraclea, the native prince Bas of Bithynia managed to defeat Alexander the Great's general Calas in battle (probably around 330 BC).

[1] His son and successor, Nicomedes I, founded Nicomedia, which soon rose to great prosperity, and during his long reign (c. 278 – c. 255 BC), Bithynia developed considerable standing and influence among the minor monarchies of Anatolia.

Bithynia remained neutral during the Roman–Seleucid War from 192 to 188 BC, despite the Seleucid Empire and its king Antiochus the Great being the long-time enemy of the kingdom.

Following Prusias II's failed invasion of the Roman ally of the Kingdom of Pergamon in 154 BC, Bithynia was forced to pay heavy war reparations.

Becoming king in 127 BC, Nicomedes III conquered Paphlagonia along the Black Sea and began to expand his influence over the Roman ally of Cappadocia.

Though the Social War was still raging in Italy, Rome was able to successfully restore both kings due to the Republic's growing influence in the region.

Nicomedes IV's death caused a power vacuum in Asia Minor, allowing Mithridates VI to invade and conquer the leaderless kingdom.

With Mithridates VI again having designs on Roman protectorates in Asia Minor, including Bithynia, Rome launched a third war against Pontus.

Recalling Lucullus, the Senate dispatched Gnaeus Pompeius Magnus ("Pompey") to the East to finally defeat Mithridates VI.

Arriving in Asia Minor in 65 BC, Pompey decisively defeated Mithridates VI in the Caucasus Mountains of Kingdom of Armenia.

As for the eastern half of Pontus ("Lesser Armenia"), Pompey added its territory to that of the Kingdom of Galatia under the Roman client king Deiotarus as a reward for his loyalty to Rome.