Tumgan (Turkshad, Turksanf, Ta'n han, Turxanthos, Turxath) was a shad (governor prince) of the Turkic Empire (also called Göktürk) in the late 6th century.According to Edward Gibbon his name may be a title rather than a proper name.
Turkic Empire was a vast empire in Asia and parts of East Europe. Up to 603, while the east part of the empire was considered as the main empire, the western part (roughly west of Altai and Tengri Mountains) was considered as the dependency of the main empire. Western part was ruled by a yabgu (Yabgu was the title of a co-khagan who was tasked to rule the western territories in behalf of the main khagan)
As a shad
Tumgan’s father was İstemi yabgu who was the younger brother of Bumin, the founder of the empire. İstemi died in 576 and he was succeeded by Tamgan and Tamgan's elder brother Tardu. Although most of the western territories were ruled by Tardu, Volga River region was under Tamgan's rule. According to Cambridge History of Inner Asia, Tardu was Tamgan's superior. (Cambridge History also questions whether or not Tardu and Tamgan were brothers.)
Relations with the Byzantine Empire
Because of the geographic position of his region, Tamgan was responsible in diplomatic relations with Byzantine Empire. (Hence, the historical sources about Tamgan are mostly the reports of Byzantine envoys). Inıtially Turkic and Byzantine Empires were allies against Sassanid Iran and Eurasian Avars. However, according to Byzantine historian Menander Protector, a Byzantine envoy named Valentinos visited Tamgan's headquarters where Tamgan accused Byzantines for the recently signed treaty between the Byzantine Empire and the Avars. He said that the Byzantines were liars and had ten tongues, meaning they were unreliable as allies. He also threatened the Byzantine side mentioning the rivers Danapr, Istr and Evr. (Former names of Dnieper, Danube and Maritsa.)  Following this accusation, Turks began to capture Byzantine possessions around north east Black Sea coasts and even Crimea. Briefly, a part of Bosporan Kingdom in Crimea, a vassal of Byzantine Empire fell to Turks. Tardu effectively fought in this area, but left his gains to Tamgan. (About half a century later Byzantine Turkic relations recovered and Turks collabrated with Heraclius in the invasion of North Caucasus.)
There is no record of Tamgan's death. However it is known that together with his brother he supported Apa Khagan during the Turkic interregnum after 584. Thus Tamgan's death year can be located to be later than 584.
- Edward Gibbon:Decline and fall of the Roman Empire Vol IV, ISBN 0-8095-9238-X p.576
- Cambridge History of Inner Asia, ISBN o 521 2,4304 1 , p.304
- L.M.Gümilev :Eski Türkler, tr:Ahsen Batur, Selenge yayınları, İstanbul, 2002, ISBN 975-7956-39-8, p.69, 141
- S.G.Klashtorny-T,I.Sultanov:Türkün Üçbinyılı (tr:D.Ahsen batur),Selenge yayınları, ISBN 975-8839-03--9, p.102