The Kingdom of Georgia also known as Georgian Empire was a medieval monarchy established in 975 by Bagrat III. The kingdom reached its Golden Age of political and economic strength during the reign of King David IV the Builder and Queen Tamar the Great from 11th to 13th centuries. It fell to the Mongol invasions of the 13th century, but managed to re-assert sovereignty by the 1340s. Renewed Turco-Mongol incursions from 1386 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. A unified Georgian state would not emerge again until 1762, when the kingdoms of Kartli and Kakheti merged to form unified Kingdom of Kartli-Kakheti. In 1801 the state was annexed by the Russian Empire and remained under Russian (and later Soviet) rule until 1991 (see Georgian SSR), when present day Georgia was founded.