Eastern Turkic Khaganate, while the Western Turkic Khaganate and Tiele used their own tribal names. Of the Tiele, the Book of Sui mentions only tribes which were not part a part of the First Turkic Khaganate. There was not a unified expansion of Turkic tribes. Peripheral Turkic peoples in the Göktürk Empire like the Bulgars and even central ones like the Oghuz and Karluks migrated autonomously with migrating traders, soldiers and townspeople. The precise date of the initial expansion from the early homeland remains unknown. The first state known as Turk, giving its name to the many states and peoples afterward, was that of the Göktürks (gök 'blue' or 'celestial', however in this context gök refers to the direction 'east'. Therefore, Gökturks only denoted the Eastern Turks in the 6th century. In 439, the head of the Ashina clan led his people from Pingliang (now in modern Gansu province, China) to the Rouran seeking inclusion in their confederacy and protection. His tribe consisted of famed metalsmiths and was granted land near a mountain quarry that looked like a helmet, from which they got the name Turk/Tujue . In 546, the leader of the Ashina, Bumin, aided the Rouran in putting down a Tiele revolt. Bumin requested a Rouran princess for his service but was denied, after which he declared independence. In 551, Bumin declared himself Khagan and married Princess Changle from Western Wei. He then dealt a serious blow to the Rouran Khaganate the next year, but died soon after. His sons, Issik Qaghan and Muqan Qaghan, continued to wage war on the Rouran, finishing them off in 554. By 568, their territory had reached the edges of the Byzantine Empire, where the Avars, possibly related to the Rouran in some fashion, escaped. In 581, Taspar Qaghan died and the khaganate entered a civil war that resulted in two separate Turkic factions. The Eastern Khaganate was defeated by the Tang dynasty in 630 while the Western Khaganate fell to the Tang in 657. In 682, Ilterish Qaghan rebelled against the Tang and founded the Second Turkic Khaganate, which fell to the Uyghurs in 744. Bulgar The Bulgars, also known as the Onogur-Bulgars or Onogundurs, arrived in the Kuban steppe zone sometime during the 5th century. By the 7th century, they were under the rule of the Avars, who they revolted against in 635 under the leadership of Kubrat. Prior to