Mithridates IV of Parthia ruled the western Parthian Empire

Parthia

Parthia is a region of north-eastern Iran, best known for having been the political and cultural base of the Arsacid dynasty, rulers of the Parthian Empire....

 from 129 to 140. He was the brother of Osroes I of Parthia

Osroes I of Parthia

Osroes I of Parthia ruled the Parthian Empire c. 109–129. He succeeded his brother Pacorus II. For the whole of his reign he contended with the rival king Vologases III based in the east of Parthia....

 (109–129). He was the youngest son of the Parthian King Vonones II. During the invasion of Mesopotamia

Mesopotamia

Mesopotamia is a toponym for the area of the Tigris–Euphrates river system, largely corresponding to modern-day Iraq, northeastern Syria, southeastern Turkey and southwestern Iran.Widely considered to be the cradle of civilization, Bronze Age Mesopotamia included Sumer and the...

 by the Roman emperor

Roman Emperor

The Roman emperor was the ruler of the Roman State during the imperial period . The Romans had no single term for the office although at any given time, a given title was associated with the emperor...

 Trajan

Trajan

Trajan , was Roman Emperor from 98 to 117 AD. Born into a non-patrician family in the province of Hispania Baetica, in Spain Trajan rose to prominence during the reign of emperor Domitian. Serving as a legatus legionis in Hispania Tarraconensis, in Spain, in 89 Trajan supported the emperor against...

 (98–117) in 116 he and his son Sanatruces II

Sanatruces II of Parthia

Sanatruces II of Parthia, the son of Mithridates IV, was a pretender to the throne of the Parthian Empire during the disputed reign of his uncle Osroes I....

 took up the diadem but were defeated. After the death of Osroes I in 129 he assumed the throne and continued the struggle with the rival king Vologases III of Parthia

Vologases III of Parthia

Vologases III of Parthia claimed the throne of the Parthian Empire about 105, in the last days of Pacorus II of Parthia . He reigned over the eastern portion of the kingdom from 105 to 147...

 (105–147). He died in an attack on Commagene in 140. Mithridates IV had appointed his son Sanatruces successor, but Sanatruces fell in a battle with the Romans. Another son, Vologases IV of Parthia

Vologases IV of Parthia

Vologases IV of Parthia ruled the Parthian Empire from 147 to 191. The son of Mithridates IV of Parthia , he united the two halves of the empire which had been split between his father and Vologases III of Parthia...

 (147–191), took the throne after the death of Vologases III in 147.