The border then proceeds to the north-west along the Karasu Çayı river, thereby granting Turkey a sliver of territory linking it to Azerbaijan.

[5][6][7][8] The Zuhab treaty stipulated that the boundary between the two empires would run between the Zagros Mountains and the Tigris River, though a precise lines was not drawn at that time.

The Ottomans and Iran agreed to work on a more precise demarcation in 1911 at the urging of Russia and the Britain, both of whom had colonial aspirations in the region.

[9] The four-nation boundary commission then surveyed the border on the ground and demarcated it with pillars (excluding the Qotur area which remained in dispute), producing a detailed series of map depicting the confirmed frontier.

As a result of the secret 1916 Anglo-French Sykes-Picot Agreement Britain gained control of the Ottoman Vilayets of Mosul, Baghdad and Basra, which it organised into the mandate of Iraq in 1920.

[9] By the 1920 Treaty of Sèvres Anatolian Turkey was to be partitioned, with the areas north of the Mosul Vilayet to be included within an autonomous or independent Kurdish state.

[9] From 2017, Turkey began construction a barrier along the Turkey-Iran border aimed at preventing illegal crossings and smuggling.

[citation needed] The Turkish government has expanded its plans to build a concrete wall along the Iranian border to cover the entirety of the frontier of 295 kilometres (183 miles), Van Governor Mehmet Emin Bilmez said on July 27, 2021.