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". The Göktürks (First Turkic Kaganate) quickly spread west to the Caspian Sea. Between 581 and 603 the Western Turkic Khaganate in Kazakhstan separated from the Eastern Turkic Khaganate in Mongolia and Manchuria during a civil war. The Han-Chinese successfully overthrew the Eastern Turks in 630 and created a military Protectorate until 682. After that time the Second Turkic Khaganate ruled large parts of the former Göktürk area. After several wars between Turks, Chinese and Tibetans, the weakened Second Turkic Khaganate was replaced by the Uyghur Khaganate in the year 744. Bulgars, Golden Horde and the Siberian Khanate The Bulgars established themselves in between the Caspian and Black Seas in the 5th and 6th centuries, followed by their conquerors, the Khazars who converted to Judaism in the 8th or 9th century. After them came the Pechenegs who created a large confederacy, which was subsequently taken over by the Cumans and the Kipchaks. One group of Bulgars settled in the Volga region and mixed with local Volga Finns to become the Volga Bulgars in what is today Tatarstan. These Bulgars were conquered by the Mongols following their westward sweep under Ogedei Khan in the 13th century. Other Bulgars settled in Southeastern Europe in the 7th and 8th centuries, and mixed with the Slavic population, adopting what eventually became the Slavic Bulgarian language. Everywhere, Turkic groups mixed with the local populations to varying degrees. The Volga Bulgaria became an Islamic state in 922 and influenced the region as it controlled many trade routes. In the 13th century, Mongols invaded Europe and established the Golden Horde in Eastern Europe, western & northern Central Asia, and even western Siberia. The Cuman-Kipchak Confederation and Islamic Volga Bulgaria were absorbed by the Golden Horde in the 13th century; in the 14th century, Islam became the official religion under Uzbeg Khan where the general population (Turks) as well as the aristocracy (Mongols) came to speak the Kipchak language and were collectively known as "Tatars" by Russians and Westerners. This country was also known as the Kipchak Khanate