In February of the fifth year of Jian 'an (AD 200), Yuan Shao sent Guo Tu, Chun Yuqiong and Yan Liang to attack Ada, the satrap of the East County stationed in Baima, and Yuan Shao led the troops to Liyang to prepare to cross the river. In April, Cao Cao went north to rescue Ada. Xun You persuaded Cao Cao: "Our troops are few now, so it is difficult to defend against the enemy. Only by dispersing their forces can we win. When you go to Yanjin, pretend that you want to cross the river and attack its rear. Yuan Shao will divide his troops for the western expedition. Then lead light troops to attack the white horse, and you can catch it while Yan Liang is unprepared. " Cao Cao adopted his suggestion. When Yuan Shao heard that Cao Jun had crossed the Yellow River, he immediately suited himself for the Western Expedition. Cao Cao led a great army to Baima day and night. When there were more than ten miles away from the white horse, Yan Liang was frightened and came to fight. Cao Cao sent Zhang Liao and Guan Yu as pioneers, defeated Yuan Jun and beheaded them. So the siege of the White Horse was lifted and the local people retreated westward along the Yellow River. Yuan Shao crossed the river to catch up with Cao Jun and the south of Yanjin. Cao Cao led his troops to camp on the southern hillside and sent people to check the enemy's situation in the camp. The report said, "There are about five or six hundred cavalry." After a while, someone reported: "cavalry is increasing gradually, and there are too many infantry to count." Cao Cao said, "Don't report any more." He ordered the cavalry to unload their saddles and let go of their horses. At this time, the ammunition collected from Baima has been transported to Kaminooji. The generals thought that the enemy had more cavalry, so it was better to withdraw from the barracks. Xun You said, "This is to lure the enemy into the bait. How can you withdraw? " Yuan Shao's cavalry generals Wen Chou and Liu Bei led five or six thousand cavalry to arrive successively. The generals in Cao Jun said, "You can get on the horse." Cao Cao said, "No."After a while, there were more and more enemy cavalry, some of whom concentrated on munitions and galloped separately. Cao Cao said, "That's enough." So they mounted their horses. There were less than 600 cavalry at that time. Cao Cao sent troops to attack, defeated the enemy and killed Wen Chou. Yan Liang and Wen Chou are both famous soldiers under Yuan Shao. After two battles, they were captured alive and killed, which shocked Yuan Shao. Cao Cao returned to the official entrance. Yuan Shao marched to defend Wu Yang. Guan Yu took the opportunity to flee to Liu Bei.