Tigranes had been a hostage until the age of 45 at the court of King Mithridates II of Parthia after the Armenian defeat in 105 BC. Other sources give the date as much earlier, at around 112–111 BC. After the death of King Tigranes I in 95 BC, Tigranes bought his freedom, according to Strabo, by handing over "seventy valleys" in Atropatene to the Parthians.
When he came to power, the foundation upon which Tigranes was to build his Empire was already in place, a legacy of the founder of the Artaxiad Dynasty, Artaxias I, and subsequent kings. The mountains of Armenia, however, formed natural borders between the different regions of the country and as a result, the feudalistic nakharars had significant influence over the regions or provinces in which they were based. This did not suit Tigranes, who wanted to create a centralist empire. He thus proceeded by consolidating his power within Armenia before embarking on his campaign.
He rapidly built up his power and established an alliance with Mithridates VI, marrying his daughter Cleopatra. Tigranes agreed to extend his influence in the East, while Mithridates set to conquer Roman land in Asia Minor and in Europe. By creating a stronger Hellenistic state, Mithridates was to contend with the well-established Roman foothold in Europe. Mithridates executed a planned general attack on Romans and Italians in Asia Minor, tapping into local discontent with the Romans and their taxes and urging the peoples of Asia Minor to raise against foreign influence. The slaughter of 80,000 people in the province of Asia Minor was known as the Asiatic Vespers. The two kings' attempts to control Cappadocia and then the massacres resulted in guaranteed Roman intervention. The senate decided that Lucius Cornelius Sulla, who was then one of the consuls, would command the army against Mithridates.
When he acquired power, he recovered these (seventy) valleys, and devastated the country of the Parthians, the territory about Ninus (Nineveh), and that about Arbela. He subjected to his authority the Atropatenians, and the Goryaeans (on the Upper Tigris); by force of arms he obtained possession also of the rest of Mesopotamia and, after crossing the Euphrates, of Syria and Phoenicea. —Strabo