on the campain against Cao Cao with lu bus forces complete the following:
Circle around behind Yue Jin's secret ambush party. To do this
you must head right and down. You'll see an ambush party of Xu Huang. Kill him, and one of your generals will inform you about other ambush parties. A flashing white dot will appear south of the castle on the left side of the map. Head down to Cao Cao's caslte and head left and up, so you are to the rear entrance of the castle. Yue Jin's ambush party will run away, after
a few minutes Xiahou Dun will appear in the empty section to the top left area of the map. Kill him and the item report should appear.