The Tang dynasty Chinese Emperors were recognized as Khagans of the Turks at least from 665 to 705; moreover, two appeal letters from the Turkic hybrid rulers, Ashina Qutluγ Ton Tardu in 727, the Yabgu of Tokharistan, and Yina Tudun Qule in 741, the king of Tashkent, addressing Emperor Xuanzong of Tang as Tian Kehan during the Umayyad expansion.