Return to the Tang Dynasty to Assist Mingjun

Twelve years of great cause. At this time, Emperor Yang of the Sui Dynasty was trapped in Jiangdu, and the world was in a prairie fire. Li Yuan is about to raise troops in Taiyuan, Wagang Li Mi is at the height of the sun, Dou Jiande, Du Fuwei and other heroes are separatist. What should the male protagonist do when he travels to this time?