Geng Yan transmigrates into the body of a low-ranking cannon-fodder soldier in the border army of Mobei. Relying on the knowledge he acquired in his previous life, he fights to survive against impossible odds. First, he uses condensation techniques to collect water, filters it to make it drinkable, and identifies the right locations to dig wells, resolving the military camp's water crisis. Then, with his geological expertise, he exposes quicksand traps and lures the enemy into an ambush, defeating an entire cavalry force of barbarian tribes despite being outnumbered. Rising from a wounded soldier to squad leader, centurion, and eventually commander of a thousand men, Geng Yan carefully navigates power struggles and conspiracies with the enemy, winning people's loyalty and building his own inner circle. He also uncovers the secret of petroleum and prepares to use fire attacks against twenty thousand barbarian cavalrymen. Meanwhile, Kong Deming, the Minister of War at court, has already burned the letter requesting reinforcements. A deadly battle that will determine the survival of the Western Camp is about to erupt.