BackgroundThe Parthians were a people that hailed from the regions of Elymais and Medea in Persia and Tribus Sakae in Russia, a group of steppe horsemen. They evolved from the old steppe nomads of Iran and Dahae, and after Dahae was conquered by Alexander III of Macedon, the Parthians lived in obscurity until 270 BC, when they gained independence from the Seleucid Empire, founded by one of Alexander's Diadochi, Seleukos.
The Parthians' first leader was Arsaces, who centered his armies around Cataphracts and horse archers. His natural foes were his immediate rivals: the Seleucid Empire, Artaxiad Empire, and Scythia. In 268 BC he defeated the Armenians at the Battle of Lasphia, followed by victories by his son and successor Ardumanish I of Parthia; he died of fever shortly after. The reign of Ardumanish was comparable to that of Sargon of Akkade, modernizing his armies and conquering almost all of the Middle East using mercenary infantry and horse-mounted archers. The Parthians later went to war with the Ptolemaic Empire when the Egyptians attacked them to halt their transgression.
Parthia eventually conquered all of Alexander the Great's Transoxanian and Persian satrapies and invaded the Levant. The Parthians had created a giant empire stretching from India to the Dead Sea by the time that they had met their mortal foes: the Roman Republic. Starting in 66 BC, the Parthians fought a series of wars with Rome, and the Battle of Carrhae in 53 was one of Rome's worst defeats, also starting the Roman Civil War. In 27 BC, when the Roman Empire was declared, the animosities continued, and a series of campaigns against Parthia (the last major one being led by Marcus Traianus (Trajan) in 119 AD). However, Parthia was destroyed in 224 AD when a military coup replaced the Parthians with the Sasanid Empire.