In the 6th century, 400 years after the collapse of northern Xiongnu power in Inner Asia, the Göktürks assumed leadership of the Turkic peoples. Formerly in the Xiongnu nomadic confederation, the Göktürks inherited their traditions and administrative experience. From 552 to 745, Göktürk leadership united the nomadic Turkic tribes into the Göktürk Empire on Mongolia and Central Asia. The original Old Turkic name "Kök Türk" derives from "kök" ~ "kö:k", "sky, sky-coloured, blue, blue-grey".. Unlike its Xiongnu predecessor, the Göktürk Khaganate had its temporary Khagans from the Ashina clan, who were "subordinate" to a sovereign authority controlled by a council of tribal chiefs. The Khaganate retained elements of its original animistic- shamanistic religion, that later evolved into Tengriism, although it received missionaries of Buddhist monks and practiced a syncretic religion. The Göktürks were the first Turkic people to write Old Turkic in a runic script, the Orkhon script. The Khaganate was also the first state known as "Turk". It eventually collapsed due to a series of dynastic conflicts, but many states and peoples later used the name "Turk".