The Long Ballad.

Li Chang Ge's family was murdered by Li Shi Min, the Emperor of Tang, during the Xuanwu Gate Incident. She heads to Shuo Province under the guise of a man with hopes of raising an army to kill Li Shi Min to avenge her family's death. However, as a captain of the army of Shuo Province in Zhangzhou, she loses a siege by the Eastern Turkic Khaganate General Ashina Sun, who takes her to serve him as a personal military strategist.