In medieval times, the region was part of the Golden Horde. After its gradual decline during the 15th century, the Khanate of Sibir, centered on Tyumen, was formed within the area. In the late 16th century, most of Western Siberia was conquered by the Russian Empire, while its southern region became part of the Kazakh Khanate. The current international borders between Russia and Kazakhstan came into being in the late 20th century following the dissolution of the Soviet Union.