During the successful reign of King David IV of Georgia (1089–1125), Kingdom of Georgia grew in strength and expelled the Seljuk Empire from its lands. David's decisive victory in the Battle of Didgori (1121) against the Seljuk Turks, as a result of which Georgia recaptured its lost capital Tbilisi, marked the beginning of the Georgian Golden Age. David's granddaughter Queen Tamar continued the upward rise, successfully neutralizing internal opposition and embarking on an energetic foreign policy aided by further decline of the hostile Seljuk Turks. Relying on a powerful military élite, Tamar was able to build on the successes of her predecessors to consolidate an empire which dominated vast lands spanning from present-day southern Russia on the Black Sea to the Caspian Sea. Georgia remained a leading regional power until its collapse under the Mongol attacks within two decades after Tamar's death.