Tamar was proclaimed heir and co-ruler by her reigning father George III in 1178, but she faced significant opposition from the aristocracy upon her ascension to full ruling powers after George's death. Tamar was successful in neutralizing this opposition and embarked on an energetic foreign policy aided by the decline of the hostile Seljuq Turks. Relying on a powerful military elite, Tamar was able to build on the successes of her predecessors to consolidate an empire which dominated the Caucasus until its collapse under the Mongol attacks within two decades after Tamar's death.