Margiana ( Margianḗ, Old Persian: Marguš, Middle Persian: Marv) is a historical region centred on the oasis of Merv and was a minor satrapy within the Achaemenid satrapy of Bactria, and a province within its successors, the Seleucid, Parthian and Sasanian empires. It was located in the valley of the Murghab River which has its sources in the mountains of Afghanistan, and passes through Murghab District in modern Afghanistan, and then reaches the oasis of Merv in modern Turkmenistan. Margiana bordered Parthia to the south-west, Aria in the south, Bactria in the east and Sogdia in the north. History Ancient period Historians currently disagree as to the exact history of Margiana prior to the Achaemenid conquest. It is considered part of a Bronze Age civilisation, the Bactria–Margiana Archaeological Complex (short BMAC), also known as the Oxus civilisation. Some historians have argued that a kingdom was established and an urban society had begun to develop surrounding the oasis. It has also been postulated the region existed as part of a major Iranian state centred in Chorasmia that controlled Aria, Sogdia, Parthia and Margiana. Other historians have noted that whilst advanced irrigation had begun in the 7th century BC, the existence of such a state is unlikely. It has been also suggested that Margiana was part of the satrapy of Bactria under the Median Empire. Achaemenid period Margiana was conquered by the Persian king Cyrus the Great between 545 and 539 BC and remained as part of the satrapy of Bactria. Cyrus also founded the city of Merv. After Darius the Great's victory over the Magian usurper, Gaumata, in September 522 BC, revolts spread throughout the empire. The revolt in Margiana, led by a certain Frâda (Phraates), was suppressed almost immediately, in December 521 BC by Dadarsi, the Satrap of Bactria. In the Aramaic version of the Behistun Inscription, it is claimed that 55,423 Margians were killed and 6,972 taken captive in the aftermath of the revolt. Margiana was separated from the satrapy of Bactria and joined to the satrapy of Aria at some point after the rule of Darius the Great. Following the Battle of Gaugamela in 331 BC, in which Alexander the Great defeated Darius III, Darius III began his retreat to Bactria, however he was overthrown by the Satrap of Bactria, Bessus, who continued the retreat eastward through Aria and Margiana. Bessus, who had expected an attack from Alexander