Play the Battle of Guan Du as the Wei forces. Defeat Wen Chou and Yan Liang to trigger Yuan Shao to appear and order a charge. Shortly after that, Guan Yu will "return to his brother's side", and Liu Bei, Zhang Fei along with Guan Yu will withdraw. After this happens, wait for your two castles/forts to fall to Yuan Shao's forces. Cao Cao will retreat into his castle. The enemy supply depot will be spotted and Cao Cao will charge up the right side path to attack it. Cover him while he moves. The castle walls should soon be destroyed by the rams. Then at the supply depot, defeat Chen Yu Quiong and Lu Wei Kuan. Continue to kill enemy troops to allow Cao Cao inside to burn the enemy supply depot. Zhang He will defect to your forces and you will get Xu Huang's level 10 weapon, the Marauder.