Play Escape From Chi Bí on the hard difficulty setting. Your task is to defeat all enemy reinforcements quickly. This means that you should be able to defeat the reinforcement before Cao Cao's own reinforcement says something along the lines of "Go on first, I'll take care of things here!". You do not need to worry about sub-generals; just get each major general as they show up. After you defeat Guan Ping, immediately go south, as Sun Quan will show up in the southeast. Once you defeat Sun Quan, the precious item box will show up in the little nook between where Zhao Yun and Zhang Fei appeared. Grab the item, then go up and defeat Liu Bei to help Cao Cao escape.