After forming an alliance with the Sassanid ruler Khosrow I to defeat the Hephthalite Empire, Istämi was approached by Sogdian merchants requesting permission to seek an audience with the Sassanid king of kings for the privilege of traveling through Persian territories in order to trade with the Byzantines.
[6] Maniah, a Sogdian diplomat, convinced Istämi to send an embassy directly to Byzantium's capital Constantinople, which arrived in 568 and offered not only silk as a gift to Byzantine ruler Justin II, but also proposed an alliance against Sassanid Persia.
Justin II agreed and sent an embassy to the Turkic Khaganate, ensuring the direct silk trade desired by the Sogdians.
As a Yabghu, he was autonomous and had de facto sovereignty while officially recognizing the authority of the qaghan.
After Khushu's death he arranged the division of the territory into three realms east, central, and west and distributed them between Jotan, Arslan, and Shetu, respectively.