After the death of Artabanus I, who was killed in a battle against the Yuezhi nomads in Central Eurasia in 122 BCE, Mithradates II became king. He would succeed in restoring order on the northeastern frontier and in Babylonia, where the city of Charax had revolted. He would also expand the Parthian Empire to the west. However, it seems that there was a brief intermezzo: there is evidence for a king who is usually called Arsaces X. He is little more than a name: in 121 BCE, the reign of Mithradates II had already begun.
The chronology of the Arsacid kings of the Parthian Empire is less well-understood than, for example, the sequence of Seleucid and Ptolemaic kings or the emperors of Rome. This information is based on the researches by G.R.F. Assar, as published in "Iran under the Arsakids, 247 BC – AD 224/227" in: Numismatic Art of Persia (2011).