Urtatagai conflict (1925–1926)
The Urtatagai conflict was a conflict between the Soviet Union and the Emirate of Afghanistan in the mid-1920s over the control of the island of Urta Tagay, which is an island on the Amu Darya river that had been claimed by Afghanistan since 1900, although it was under Russian control until 1920, when remnants of the Imperial Russian Army evacuated the island to aid the White movement in the Russian Civil War. The Afghan Army had earlier unsuccessfully tried to enforce its claim on Urtatagai in a border conflict in 1913, and in 1920 Afghan forces were finally able to capture the island unopposed.
Source: Wikipedia — Urtatagai conflict (1925–1926) (CC BY-SA 4.0)