Lasting for several centuries, the kingdom fell to the Mongol invasions in the 13th century, but managed to re-assert sovereignty by the 1340s. The following decades were marked by the Black Death, as well as numerous invasions under the leadership of Timur, who devastated the country's economy, population, and urban centers. The Kingdom's geopolitical situation further worsened after the fall of the Byzantine and then Empire of Trebizond. As a result of these processes, by the end of the 15th century Georgia turned into a fractured entity. Renewed incursions by Timur from 1386, and the later invasions by the Kara Koyunlu and Ak Koyunlu led to the final collapse of the kingdom into anarchy by 1466 and the mutual recognition of its constituent kingdoms of Kartli, Kakheti and Imereti as independent states between 1490 and 1493 – each led by a rival branch of the Bagrationi dynasty, and into five semi-independent principalities – Odishi, Guria, Abkhazia, Svaneti, and Samtskhe – dominated by their own feudal clans.