Following the death of Alexander and the breakup of his empire, Anatolia was ruled by a series of Hellenistic kingdoms, such as the Attalids of Pergamum and the Seleucids, the latter controlling most of Anatolia. A period of peaceful Hellenization followed, such that the local Anatolian languages had been supplanted by Greek by the 1st century BC. In 133 BC the last Attalid king bequeathed his kingdom to the Roman Republic, and western and central Anatolia came under Roman control, but Hellenistic culture remained predominant. Further annexations by Rome, in particular of the Kingdom of Pontus by Pompey, brought all of Anatolia under Roman control, except for the eastern frontier with the Parthian Empire, which remained unstable for centuries, causing a series of wars, culminating in the Roman-Parthian Wars.