In the ninth year of Wude, Li Shimin, the second son of Emperor Gaozu of Tang and King of Qin, ascended to the highest ruling position of the Tang Dynasty after the Incident at Xuanwu Gate, becoming the second emperor of the Tang Dynasty, historically known as Taizong. The leader of the northern grassland nomads, Jiali, had always been eyeing the fertile lands of Central China. Taking advantage of the instability after Emperor Taizong's recent enthronement, Jiali personally led an army of two hundred thousand iron cavalry to threaten Chang'an, bringing the troops to the city gates and plunging the Tang Dynasty into turmoil. In this critical moment of national and ethnic survival, Li Shimin, with his strong character and military prowess, remained calm amidst chaos and personally led six riders to the Weishui Bianqiao, forcing Jiali's army to retreat. Li Shimin carefully analyzed the situation, overcame opposition, and made the difficult decision to deplete the state treasury to negotiate peace with the powerful Jiali in order to buy time for the country to recover and develop, thus avoiding the risk of national collapse. With great ambitions and a resilient character, Emperor Taizong of Tang was determined to quickly lead his soldiers, officials, and people to revitalize the Tang Dynasty, conquer the Jiali tribe that had dominated the north for many years, and achieve national unity.