Play the Battle Of Mai Castle level on the Wu side. First, allow Liao Hua to escape from the battle. Enter the castle through the northern gate. Kill Jiang Wei's Sub-General Wan Fu. Then, kill the Gate Captain at the north wall, then the one at the south wall. Liao Hua will return with additional troops. Destroy them, including the Sub-General in the group. Return to the castle and kill Guan Ping. This causes Guan Yu to attempt an escape. This is why the two Gate Captains had to be killed; he will try to escape to one of them if they are not sealed. Kill the northern-most Gate Captain. Guan Yu will change direction and head for the southern-most Gate Captain. Once both of those are shut off, go back into the castle and an ambush troop will appear. Destroy them. Zhang Fei should appear soon, if not already. Eliminate all Generals and Sub-Generals (besides Guan Yu). Kill Zhang Fei and you should then receive the White Tiger. Finish the level.