The Battle of Talas was an armed confrontation between the Abbasid Caliphate along with the Tibetan Empire against the Tang dynasty and its allies in 751. In July of that year, the Tang and Abbasid armies clashed at the Talas River over control of the regions surrounding the Syr Darya. The Tang army under Gao Xianzhi was defeated by the Abbasid army under Ziyad ibn Salih and Karluk mercenaries. Sources differ on whether the Karluks defected to the Abbasids or if they were Abbasid allies from the start. The defeat marked the end of Tang influence in Transoxiana and halted Tang westward expansion.