Start off by going up the nearby stairs and dropping down to where enemy soldiers are running around. Some officers may drop by for a visit, so politely show them the way to the ground, then go to the northwest corner and defeat the officer there to open the western path. Go down the western path and when you get to the designated spot, an ambush will happen.
The ambush will consist of Ling Tong and Gan Ning, as well as two other officers, so take them all out and then start heading to the east. Some reinforcements might show up (Han Dang and Ding Feng) to the far south, but keep heading to the spot at the west. In order to get the ladders needed to climb up, clear the nearby base of any officers to free the engineers.
Climb up the ladders and keep going until you encounter Taishi Ci. Take him out and then keep going south, destroying the bridge by going into the highlighted circle on the ground and pressing the correct button. You must now capture three bases surrounding the Wu main camp, so go back the way you came and capture the northern one.
Go west and south, then go and take the western base and then go after the southern one last. Wu's main camp will now be open, where you get to meet Zhou Tai and another officer, as Sun Quan is withdrawing from the area. Take out both and then pursuing Sun Quan. Defeating him will put an end to this battle.