Mithridates II was crowned king after the abrupt death of his predecessor Artabanus I. Inheriting a declining empire that was reeling from military pressure in both the east and west, Mithridates II quickly stabilized the situation in Mesopotamia by gaining the allegiance of Characene, and subduing the insurgent Kingdom of Elymais and also the Arabs, who had continuously raided Babylonia.

Under Mithridates II, the Parthian Empire at its zenith extended from Syria and the Caucasus to Central Asia and India.

[4] The role of Mithra peaked under the Parthians, which according to the modern historian Marek Jan Olbrycht, "seems to have been due to Zoroastrian struggles against the spread of foreign faiths in the Hellenistic period.

[8] Mithridates II quickly gained the allegiance of the Characenean ruler Hyspaosines, who had originally fought the Parthians, and briefly seized Babylon in 127 BC.

[9] Hyspaosines returned the wooden throne of Arsaces[clarification needed] to Mithridates II as a gift to the god Bel.

[10] Mithridates II now turned his eyes on Elymais, which had been originally under direct Parthian rule, but had been seized by the independent Elamite king Pittit after Artabanus I's death.

[15] In c. 120 BC, Mithridates II invaded Armenia and made its king Artavasdes I acknowledge Parthian suzerainty.

[19] In the spring of 119 BC, a Parthian force inflicted a defeat on the Arabs, which was heavy enough to make them stop their raids for a period.

[15] The Seleucid realm was at this time frail and entangled in ceaseless internal strifes and struggles for power against the Nabataeans, various local kings, Jews, and Greek cities in Syria and Phoenicia.

[22] Control over the middle Amu Darya including Amul was vital for the Parthians, in order to thwart incursions by nomads from Transoxiana, particularly from Sogdia.

[23] Parthian coins continued to be minted in western Bactria and in the middle Amu Darya until the reign of Gotarzes II (r. 40–51 AD).

[28] After Sakastan was incorporated back into the Parthian realm, Mithridates II rewarded the region to the Surenid general as his fiefdom.

[27] Tigranes remained a hostage at the Parthian court until c. 96/95 BC, when Mithridates II released him and appointed as the king of Armenia.

[31] Tigranes' daughter Ariazate had also married a son of Mithridates II, which has been suggested by the modern historian Edward Dąbrowa to have taken place shortly before he ascended the Armenian throne as a guarantee of his loyalty.

[32] The following year, Mithridates II attacked Adiabene, Gordyene and Osrhoene and conquered these city states, shifting the western border of the Parthian realm to the Euphrates.

[37] The strength and welfare of the empire under Mithridates II has been described by one Chinese traveler as the following: "Anxi [Parthia] is situated several thousand li west of the region of the Great Yuezhi.

Tiaozhi [Mesopotamia] is situated several thousand li west of Anxi [Parthia] and borders the western sea [the Persian Gulf].

It is referred to as a "Dark Age" due to the lack of clear information on the events of this period in the empire, except a series of, apparently overlapping, reigns.

[49] Since the early 2nd-century BC, the Arsacids had begun adding obvious signals in their dynastic ideology, which emphasized their association with the heritage of the ancient Achaemenid Empire.

[15] At the start of his reign, Mithridates II briefly used the Greek title Soter ("Saviour"), which was used on his coin mints in Ecbatana and Rhages.

[51] The early Arsacid monarchs are depicted on the obverse of their coins with a soft cap, known as the bashlyk, which had also been worn by Achaemenid satraps.

[53] Media, a region in central Iran which neighboured Parthia, was an important part of the Parthian realm under Mithridates II.

[60] Mithridates II is viewed favourably by both ancient and modern historians, who consider him one of the greatest and successful Parthian monarchs to ever rule.

[61] Justin says the following about him; "He was succeeded by his son Mithridates, to whom his achievements procured the surname of Great; for, being fired with a desire to emulate the merit of his ancestors, he was enabled by the vast powers of his mind to surpass their renown.