While the Han court was in chaos, Dong Zhuo marched his 200,000 battle-hardened Xiliang troops into the capital, Luoyang. He forced Emperor Liu Bian to abdicate, installed Liu Xie as Emperor Xian, and appointed himself Prime Minister. As he rode roughshod over the emperor, manipulated power for personal gain, and acted with extreme cruelty, all ministers and generals sought to eliminate him.
Cao Cao, a resourceful military officer, had long plotted to assassinate Dong Zhuo. One day, he visited Dong Zhuo with a borrowed dagger. Dong was sitting in his bedroom, with his formidable stepson, Lü Bu, standing guard nearby. When Dong Zhuo inquired about his lateness, Cao Cao replied, "My horse was slow." Cao Cao thought, "Now is your time to die," but fearing resistance from the still-powerful Dong Zhuo, he waited for the right moment.
Dong Zhuo, being a large man, grew tired from sitting and lay down facing inward. Seizing the opportunity, Cao Cao unsheathed the dagger. However, Dong Zhuo happened to see the movement in a mirror. He turned and asked Cao Cao what he was doing. Just then, Lü Bu returned with a horse. Thinking quickly, Cao Cao fabricated a story: "I chanced upon an extraordinary blade and wished to present it to you, Prime Minister." The dagger was indeed extremely sharp and about twenty centimeters long. Pleased, Dong Zhuo instructed Cao Cao to inspect a newly selected horse.
Outside, Cao Cao requested a test ride. He then leaped onto the horse and galloped away. "He must have come to murder me," Dong Zhuo said to Lü Bu. "I agree," Lü Bu echoed. They immediately dispatched soldiers in pursuit, but by then, Cao Cao had already fled through the eastern gate.