The next ruler of Bithynia,
Nicomedes IV, was a figurehead manipulated by the Romans. Mithridates plotted to overthrow him, but his attempts failed and Nicomedes, instigated by his Roman advisors, declared war on Pontus. Mithridates invaded Bithynia and promptly overran the country, leading his troops all the way to the
Propontis.
The kingdom Pontus comprised a mixed population in its
Ionian Greek and Anatolian cities. The royal family became fully hellenised after the capital was moved to the Greek city of Sinope. Its rulers tried to fully assimilate the potential of their subjects by showing a Greek face to the Greek world and an Iranian/Anatolian face to the Eastern world. Whenever the gap between the rulers and their Anatolian subject became greater, they would put emphasis on their Persian origins. In this manner, the royal propaganda claimed heritage both from Persian and Greek rulers, including
Cyrus, Darius I, Seleucus I and
Alexander the Great. Mithridates too posed as the champion of
Hellenism, but this was mainly to further his political ambitions; it is no proof that he felt a mission to promote its extension within his domains. Whatever his true intentions, the Greek cities (including
Athens) defected to the side of Mithridates and welcomed his armies in mainland Greece, while his fleet besieged the Romans at
Rhodes.
Tigranes II, king of neighboring
Armenia, established an alliance with Mithridates and married the Pontic leader's daughter,
Cleopatra. They would support each other in the coming conflict with Rome.
After conquering western
Anatolia in
88 BC, Mithridates VI reportedly ordered the killing of all Romans living there. The alleged massacre of 80,000 Roman men, women and children in an incident known as the
Asiatic Vespers brought matters to a head. During the
First Mithridatic War fought between
88 BC and
84 BC, Lucius Cornelius Sulla forced Mithridates VI out of Greece proper but then had to return to
Italy to answer the threat posed by
Gaius Marius; subsequently, Mithridates VI was defeated but not beaten. A peace was made between Rome and Pontus, but this proved a mere temporary setback.
Mithridates recouped his forces, and when Rome attempted to
annex Bithynia, Mithridates VI attacked with an even larger army, leading to the
Second Mithridatic War from
83 BC to
82 BC. First
Lucullus and then
Pompey the Great were sent against Mithridates VI, who was at last defeated by Pompey in the
Third Mithridatic War of
75 BC to
65 BC.
After his final defeat in 65 BC, Mithridates VI fled to
Crimea and attempted to raise yet another army to take on the Romans but failed to do so. In 63, he withdrew to the citadel in
Panticapaeum. Later he marched north with a small number of men. At Colchis he commandeered a fleet and went to his eldest son, Manchares, the king of
Cimmerian Bosporus. However, when he arrived he found his son had betrayed him. Manchares committed suicide and Mithridates took the throne of the
Bosporan Kingdom. Mithridates ordered the conscription of many
Scythians in order to regain his kingdom.
Pharnaces II, his younger son, led a new Scythian rebellion against his father. This rebellion was stirred by Roman exiles that Mithridates kept as the core of his Pontic army.