In the Battle of Hanzhong, why did Cao Cao take the initiative to withdraw his troops?

Although Cao Cao's initiative to retreat was affected by external environmental factors, such as the critical situation on the northwest border, the military pressure in Jingzhou on the center line, and the impact of internal rebellion, the main reason was that Cao Cao was no longer able to retreat due to huge logistical pressure. The confrontation between Hanzhong and Liu Bei continued. Xia Houyuan was killed in the first month of 219 AD. In fact, Cao Cao had arrived in Chang'an in September 218. After arriving in Chang'an, Cao Cao did not go south to Hanzhong to support Xia Houyuan. Instead, he sat in Chang'an and observed the situation.

Why didn't Cao Cao immediately go south to Hanzhong to support Xiahou Yuan? Because Cao Cao had more important things, and Cao Cao believed that as long as Xia Houyuan held on correctly, Liu Bei would not be able to take advantage in Hanzhong. In fact, the Battle of Hanzhong started in 217, and in the past two years, Liu Bei had not taken advantage. Cao Cao was actually on his way to Chang'an from Yecheng. Daibei Wuhuan Wuchendi and other tribes passing through the northwest of Cao Wei rebelled. Cao Cao had sent Cao Zhang to suppress it. Before the situation in the northwest was completely clear, in October 2018, Jingzhou There was a rebellion in Wancheng. Wei Kai and Hou Yin, the guards of Wancheng, could not bear Cao Wei's excessive taxes and miscellaneous taxes, so they rebelled in the city. Cao Cao sent Cao Ren to quell the rebellion in Wancheng. Cao Ren had just put down the rebellion in Wancheng in the first month of 219, and ended up in Hanzhong. News came from the front line that Xia Houyuan had died in battle.

Originally Liu Bei did not gain any advantage in the Battle of Hanzhong. If he attacked Hanzhong from Baishui Pass from Chengdu, Yangping Pass was the first pass. If Yangping Pass could not be taken, Liu Bei would not be able to take Hanzhong, but Liu Bei Starting from the first month of 219, Liu Bei changed his tactics. He climbed over the roadless Micang Mountain and appeared on the east side of Yangping Pass, behind Xia Houyuan. Liu Bei lured Xia Houyuan into battle, and then used a strategy to kill Xia Houyuan in one fell swoop. So Cao Cao led his army and rushed to Hanzhong. After a month's march, Cao Cao walked through the 500-mile Baoxie Road and entered Hanzhong. Then he entered Yangping Pass along the Han River and began to confront Liu Bei. However, Liu Bei refused at this time. Go to war.

The location of Dingjun Mountain where Liu Bei is stationed is very good. It is on the south bank of the Han River between Yangping Pass and Cao Cao's grain road. If Cao Cao wants to use the Han River to transport grain, he must pass through Liu Bei's Dingjun Mountain. In order to prevent Liu Bei from attacking his camp, Cao Cao also sent troops to Dingjun Mountain to confront Liu Bei. At the same time, the two sides were also attacking each other's food roads. Not long after Cao Cao arrived at Yangping Pass, he began to move the people of Hanzhong to Guanzhong and the Central Plains. There are five roads from west to east from Guanzhong to Hanzhong, namely: Qishan Road, Chencang Road, Baoxie Road, and Tangluo Road. Road, Ziwu Valley Road. How many people did Cao Cao move away? It is said that there were at least 300,000 people.

In troubled times, population is the primary productive force and the foundation of everything. At that time, there was no shortage of land, but there was a shortage of people. With population, everything was available, so Cao Cao often did this kind of thing, relocating the population, three The migration of 100,000 people is not an easy task. It is a very difficult and complicated project for so many people to pass through these five roads to Guanzhong. In fact, these people are not willing to move. If they move, they will lose a lot of things. They will lose all their land and houses. They will have to take their livestock, food, grass, and treasures with them. It can be imagined that 300,000 people passed through those narrow passages. What a complicated project. These people need to eat. Cao Cao can't let them starve to death, so he has to provide food and grass. This is what caused Cao Cao's collapse.

At the end of the Battle of Hanzhong, Cao Cao and Liu Bei attacked each other's grain roads. As a result, Cao Cao failed, but Liu Bei successfully attacked Cao Cao's grain roads at the Han River. This suddenly made Cao Cao Unable to bear it, the food supply for so many people was suddenly tightened, and many soldiers fled with the migrants for days. Moreover, in order to ensure the smooth relocation of these 300,000 people, the increased cost burden will all fall on the farmers in the border areas of Cao Wei. More exorbitant taxes and miscellaneous taxes will make the people even more dissatisfied. Cao Cao really can't survive in Hanzhong.

On the one hand, soldiers fled every day, the morale of the army was unstable, and the war was at a stalemate; on the other hand, the huge logistical pressure made Cao Cao breathless. If this continues, it will trigger greater opposition in the Guanzhong area. wave. Finally, Cao Cao has moved most of the people in Hanzhong. Hanzhong is not of great significance to Cao Cao, not to mention the eight hundred miles of Qinchuan that is very difficult to walk between Hanzhong and Guanzhong!

In May 219, news came from the front line of Jingzhou that Guan Yu was advancing step by step, so Cao Cao finally withdrew his troops. On the way to withdraw, even the 300,000 people had not withdrawn yet. Cao Cao The retreat was also chaotic, with soldiers and civilians mixed together, and no one knew how many people died on the way.