Three Kingdoms: My Father Is Guan Yu, Forever Guarding the Realm

At the Battle of Xiangyang and Fancheng, Guan Yu captured Yu Jin, killed Pang De, routed Cao Cao's army, and shook all of China. But Sun Quan of Jiangdong launched a surprise attack on Jiangling and Gong'an, leaving Guan Yu caught between two fronts. With defeat looming, history's tragedy seemed set to repeat itself. Guan Xing transmigrates into this world, captures Xu Huang alive, kills Cao Ren, and strikes fear into all three armies. He recruits famous generals and beautiful women, develops modern military forces, and builds the greatest iron army. He conquers Jiangdong, takes Shu Han, defeats Wei, and unifies the realm. Guan Xing only meant to save his father. Somehow, he ended up conquering the world.