Peter B. Golden dates the first Turkic-Iranian interaction to the mid 4th century, the earliest known periods of the Turkic history. The origins of the First Turkic Khaganate is associated with Iranian elements. The Sogdian influence on the state was considerable. The Sogdians, international merchants of long standing with numerous trading colonies along the silk route, needed the military power of the Turks. Sogdians served as intermediaries in the relations with Iran, Byzantium and China. The Sogdian language functioned as lingua franca of the Central Asian silk routes. The Uyghur Khaganate that succeeded the Turkic Empire was even more closesly associated with Sogdian elements. After the fall of the Uyghur nomadic state, many Turkic peoples moved to Turkestan, then a predominantly Iranian and Tokharian region, which became increasingly Turkicized.
