When Kul Tigin was 26 years old, in the winter of 710 or 711, the Göktürk army set out for the Kyrgyz campaign. Kul Tigin and Bilge Qaghan also joined this expedition, the army was led by Tonyukuk. The Göktürk army which overcame the snow-covered Kögmen yiş[2] on foot, through Ak Termil[3] where only one person could pass at a time, by rolling down. They overcame obstacle on the mountain in ten days and went down the Ani Suyu. They arrived for a night attack on the Kyrgyz. According to Gumiliev, the reason why Tonyukuk, Kul Tigin and Bilge Qaghan made a night attack was that the Kyrgyz had a well-armed, 80,000 strong army and had enough hay for their horses.[4] In the battle, Kul Tigin mounted the white stallion of Bayirku, whom they had beaten before, and attacked, killing many soldiers. During these attack, the Kyrgyz attacked Kul Tigin's horse by "breaking his thigh they shot". At the end of the battle, the Kyrgyz were defeated and the Kyrgyz Khagan was killed, "the province was taken" and the Göktürks returned to Ötüken.[5]