thumb|upright|The siege of Ganja Fortress in 1804 during the Russo-Persian War of 1804–1813The area to the north of the Aras River was Iranian territory until Russia occupied it in the 19th century. About a decade later, in violation of the Gulistan treaty, the Russians invaded Iran's Erivan Khanate. This sparked the final bout of hostilities between the two, the Russo-Persian War of 1826–1828. The resulting Treaty of Turkmenchay forced Qajar Iran to cede sovereignty over the Erivan Khanate, the Nakhchivan Khanate and the remainder of the Talysh Khanate. After the incorporation of all Caucasian territories from Iran into Russia, the border between the two was set at the Aras River.
thumb|upright|The siege of Ganja Fortress in 1804 during the Russo-Persian War of 1804–1813The area to the north of the Aras River was Iranian territory until Russia occupied it in the 19th century. About a decade late,r, in violation of the Gulistan treaty the Russians invaded Iran's Erivan Khanate. This sparked the final bout of hostilities between the two, the Russo-Persian War of 1826–1828. The resulting Treaty of Turkmenchay forced Qajar Iran to cede sovereignty over the Erivan Khanate, the Nakhchivan Khanate and the remainder of the Talysh Khanate. After the incorporation of all Caucasian territories from Iran into Russia, the border between the two was set at the Aras River.