Liu Heita
The Göktürks reached their peak in late 6th century and began to invade the Sui Dynasty of China. However, the war ended due to the division of Turkic nobles and their civil war for the throne of Khagan. With the support of Emperor Wen of Sui, Yami Qaghan won the competition. However, the Göktürk empire was divided to Eastern and Western empires. Weakened by the civil war, Yami Qaghan declared allegiance to Sui Dynasty. When Sui began to decline, Shibi Khagan began to assault its territory and even surrounded Emperor Yang of Sui in Siege of Yanmen (615 AD) with 100,000 cavalry troops. After the collapse of Sui dynasty, the Göktürks intervened in the ensuing Chinese civil wars, providing support to the northeastern rebel Liu Heita against the rising Tang in 622 and 623. Liu enjoyed a long string of success but was finally routed by Li Shimin and other Tang generals and executed. The Tang dynasty was then established.