Iran–Turkmenistan border

Atrek, Kopet Dagh and Harirud

Russian conquests east of the Caspian reached Persia’s settled lands by 1869, when an agreement made the lower Atrek the border; it was extended east past Ashgabat in 1881 and to Afghanistan in 1893. By a 1921 treaty the oasis of Firyuza was to go back to Persia, but the exchange never took place, and in the 1950s Soviet possession of it was upheld.^[1]

From salt flats below sea level where the shrinking Caspian has left the Atrek’s mouth inland, the line follows the Atrek, then the Kopet Dagh ridges, with Ashgabat and the Trans-Caspian railway in the oases just north and Mashhad, the holy city of Shia Islam, beyond the mountains to the south. Near Sarakhs it drops to the Harirud and follows it to Afghanistan. Turkmen live on both sides.^[1]

A shared dam, drying

Iran and Turkmenistan jointly built the Dusti, or Friendship, Dam on the Harirud where it forms their border; it began operating in 2004 and irrigates some 25,000 hectares.^[2] Mashhad draws on it too. After the Taliban began filling the Pashdan Dam upstream in Afghanistan and opened its power station in August 2025, Iranian media said the Doosti Dam had nearly dried up. The Taliban say the Pashdan Dam will irrigate 13,000 hectares in Herat; Iranian officials called it a violation of Iran’s customary rights.^[3]