After the early-feudal Mongolian state had broken down in the 14th century, the territory of modern Bashkortostan became divided between the Kazan and Siberia Khanates and the Nogai Horde. The tribes that lived there were headed by "bi" (tribal heads). After Kazan fell to Ivan the Terrible in 1554–1555, representatives of western and northwestern Bashkir tribes approached the Tsar with a request to voluntarily join Muscovy.