In the sixteenth year of Jian'an (211), Cao Cao sent Zhong Xuan to attack in order to eliminate the princes Zhang Lu who were entrenched in the Hanzhong area, and at the same time ordered Xiahou Yuan to send troops to support (Note 1), but at that time, Cao Cao's territory did not border Hanzhong, and it was only possible to pass through Guanzhong, but this directly threatened the interests of Ma Chao and other princes in Guanzhong.

At that time, Ma Chao, Han Sui and other princes of Liangzhou and Guanzhong thought that Cao Cao was preparing to attack the Emperor with a false way, so they rebelled.

【Changes in Guanzhong】

In March of the sixteenth year of Jian'an (211), Cao Cao sent Zhong Xuan to conquer Zhang Lu, and ordered Xiahou Yuan and others to send troops from Hedong County to join Zhong Xuan. Gao Rou reminded Cao Cao for this: "When the army goes west, Han Sui, Ma Chao and others will definitely suspect that they are attacking themselves, and they will definitely incite each other." It is advisable to pacify Sanfu (Guanzhong) first, Sanfu (Guanzhong) is pacified, and Hanzhong can be pacified as long as the text is transmitted. It's a pity that Cao Cao ignored it and still sent Zhong Xuan to send troops, at that time Guanzhong was mainly Ma Chao's territory, so he reacted very fiercely to this, and even disregarded the safety of his father Ma Teng and his brother, and took the lead in uniting Han Sui and others to rebel.

According to the record of "Wei Luo", at that time, in order to win over the Liangzhou veteran Han Sui to oppose Cao, he said to Han Sui, "The former lieutenant Zhong Xuan, let me attack and annex General Han, and the words of the Kwantung people can no longer be believed, and now in order to resist Cao Cao's annexation of us, I decided to give up my father and take General Han as my father, and General Han should also give up his son and take Chao as his son." ”

Han Sui's subordinate Yan Xing advised Han Sui not to listen to Ma Chao's words and confront the imperial court, but Han Sui said: "The generals in Guanzhong coincide, and it seems that it was arranged by God. ”

Under the leadership of Han Sui and Ma Chao, the warlords of Guanzhong and Liangzhou rebelled one after another, in addition to Ma Chao and Han Sui, there were also Hou Xuan, Cheng Yin, Yang Qiu, Li Kan, Zhang Heng, Liang Xing, Cheng Yi, Ma Wan and others also responded, and at least more than ten princes rebelled. They gathered a mixed army of 100,000 Qiang, Hu, and Han people, camped in Tongguan, and prepared to attack, and many counties and towns of Hongnong and Fengyi responded with troops, and the people fled from the Meridian Valley into Hanzhong.

During this period, Ma Chao also co-opted Liu Xiongming's forces, but was refused, and he was defeated by Ma Chao's troops, and then took refuge in Cao Cao.

In order to quell the rebellion in Guanzhong and Liangzhou, Cao Cao first took Cao Ren as the general of Anxi, and supervised the generals to refuse Tongguan, Cao Cao warned the generals: "The Guanxi soldiers are brave and strong, you stick to the camp and do not fight with them." In the autumn and July of the same year, Cao Cao left Cao Pi to guard Yecheng and personally unified the army to the west.

According to the Book of Wei, many people at that time believed: "The Kansai army is strong, and it is good at using spears, if it is not a selected striker, it cannot be resisted." Cao Cao believed: "The initiative in the war lies with me, not with the enemy." Although the enemy is good at spears, I will make them not stab, so look. ”

In this way, what was originally a crusade against Zhang Lu turned into a decisive battle between Cao Cao and the princes of Guanzhong.

[Easy to defend but difficult to attack]

Guanzhong in the late Han Dynasty is actually "Sanfu", referring to the "Jing Zhao Yin", "Zuo Feng Yi" and "Right Fufeng" in the west of Sili, of which the capital Chang'an is in Jing Zhaoyin, which has always been the political and economic center of the Qin and Han dynasties.

And here there is a saying of "one hundred and two Qin Pass" since ancient times, what does it mean? That is to say, with the dangerous terrain in Guanzhong, with 20,000 soldiers, it can resist the attack of a million troops, and it is an easy place to defend and difficult to attack.

Guanzhong has always been a place of four stops, with the steep Qinling Mountains in the south, the protection of Tongguan and the Yellow River in the east, the lofty mountains of Longshan and Liupan Mountain in the west, and the Meridian Ridge and Huanglong Mountain on the plateau in northern Shaanxi in the north.

Cao Cao was able to attack Guanzhong in three main ways:

1. North Road: Go out of the east of the river, cross the Yellow River from Pubanjin to the west;

2. Middle Road: Along the main road, enter through Tongguan;

3. South Road: Go south to Wancheng first, detour to Wuguan and Lantian to enter in a roundabout way. Since the Qin Empire unified China based on Guanzhong, Gaozu of the Western Han Dynasty also unified the whole country according to the geographical advantages of Guanzhong.

In particular, attacking Guanzhong from the Central Plains in the east is basically an unfavorable situation of attacking from the back, especially the Tongguan. Therefore, if Cao Cao wants to break through the Mahan group, which occupies a dangerous position in Guanzhong, has strong troops, and has strong combat power, it is not a good choice to fight hard.

【Comparison of military strength】

At that time, Cao Cao's army was the attacker, and the Ma-Han coalition army was mainly defensive, but Cao Ren was mainly defensive in Tongguan before Cao Cao's arrival.

Within the coalition army of Ma Han Guanzhong, Ma Chao as the landlord was the core initiator of the coalition army, and Han Sui was the veteran at that time, but although he also participated in the war, he came as a support and needed to mobilize troops from Liangzhou itself, so in general, Han Sui's troops may not be as good as Ma Chao, and both of them should each have more than 10,000, or even close to 20,000 troops (Ma Chao led the main force of more than 10,000 soldiers to attack the Cao army that crossed the river many times), and the other eight were all small and medium-sized warlords, Among them, it is recorded that Liang Xing had 5,000 people (Liang Xing had led 5,000 people in his headquarters to counterattack Xu Huang, who was smuggled into Pubanjin, and he was one of the smaller ones). It is estimated that the strength of the middle warlords such as Hou Xuan, Cheng Yin, and Yang Qiu is between 5,000 and 10,000, and the strength of the latter five small warlords is about 5,000 each. Therefore, it is estimated that the actual strength of the Guanzhong coalition army is more than 80,000, or even 80,000, and it is claimed to be 100,000 (this is recorded in the Zizhi Tongjian).

And they are not all on the Tongguan front, and it is estimated that there will be some troops in the rear. In this way, about 65,000-70,000 troops actually participated in the battle against Cao's army.

There is no record of Cao Cao's participation in the battle, but it is analyzed according to the main generals and Cao Yong's habits: the generals participating in the battle: Cao Cao, naturally led his elite tiger and leopard cavalry troops to participate in the battle, with a strength of about 5,000 (Xu Zhen, Cao Zhen, and Cao Xiu were among them); General Anxi: Cao Ren, who once fought alone against the Ma-Han coalition army in Tongguan for more than three months, will not have a small number of troops (according to the fact that after this war, he sent his Seventh Army to crusade against the rebellious Su Bo and Tian Yin), it is estimated that there are about 30,000 people; Expedition to the West: Xiahou Yuan, Xu Huang, Zhu Ling and other generals were all under his control, with a strength of about 10,000; General Pingdi: Zhang He, with a strength of about 5,000 (from Poma, Han to Weinan); General Yokono: Xu Huang, with more than 4,000 troops (so that Huang crossed Tianjin with 4,000 people on foot); In addition, General Du Hu (perhaps General Li Feng) Cao Hong is also very likely to participate in the war, with a strength of about 5,000. Others: General Zhu Ling, Captain Ding Fei, etc., Captain Zhong Xuan of Sili was in Chang'an, had no troops, and did not participate in the war. In this way, the total strength of Cao Cao's troops was roughly around 60,000-65,000. Therefore, the battle was basically a battle in which the two sides were equal in strength (Note 2).

However, Cao Cao's troops have a unified command, while the princes of Guanzhong are mixed and inconvenient to command, so Cao Cao's military strength is stronger overall.

Note 1: In the same year, Liu Zhang asked Liu Bei to go north into Sichuan to crusade against Zhang Lu because of Cao Cao's crusade against Zhang Lu, which helped Liu Bei a lot.

Note 2: The last two articles are all seen in the encyclopedia, not by me, I think they are very accurate, so I borrowed them.