In the cold weapon era in China's history, there were many cases in which the north and the south ruled by crossing the river, and there were also many battles of reunification between the north and the south. Among them, Emperor Wendi of the Sui Dynasty was defeated by Cao Cao in Chibi, Emperor Sima Yan of the Jin Dynasty unified the Three Kingdoms, and the battle under the water of former Qin Emperor Fu Jian. Some of these battles ended in the unification of the north, while others ended in the successful defense of the south.

So, what is the key to the success or failure of these major battles in history? Why do some northern regimes seem to be extremely powerful, but they will fail in the process of unifying the whole country?

One of the most important decisive factors is the control of Bashu (Sichuan) area.

There are three main reasons why Sichuan is so important.

First: Bashu area controls the upper reaches of the Yangtze River waterway, and the defense of crossing the river is very important for the southern regime. If we lose Bashu, it is basically equivalent to losing the natural barrier of the Yangtze River;

Second: Since the Qin and Han Dynasties, the construction of Dujiangyan has made Sichuan Basin a real land of abundance, which can provide a lot of grain and grass. In the ancient cold war era, adequate food and grass was the key factor of military action.

Third: Bashu area is easy to defend but difficult to attack, but it is of great strategic significance to send troops directly to take Hanzhong and Chang 'an.

Next, let's count several major battles in history along the historical context and feel the vital role of Bashu in controlling the world.

1. Battle of Qin Chu (warring sides: Qin vs. Chu, winner: Qin)

As early as the end of the Warring States Period, Xiang of the State of Qin had discussed with Yi Chang and Sima Cuo whether to cut Korea or Shu first. Yi cheung thinks that Korea should be cut first, and Sima Cuo thinks that Shu should be cut first. The two sides started a debate. In the end, Zhao Haoqi followed Sima Cuo's advice and wiped out Bashu in a short time.

Later, it was proved that Qin Zhaowang chose the right plan. Although the land of Bashu was remote at that time, it became a solid granary and recruiting ground behind Qin State, which provided a strong material and human foundation for Qin State to unify the six countries. Later, Qin launched a 600,000-strong army at one time in the campaign to destroy Chu, and Wang Jian held his ground for one year, and he was able to get enough food and grass, which had a very important relationship with Shu's powerful rear supply.

2.？ Battle of Red Cliffs. (warring sides: Cao Wei VS Soochow, winner: Soochow)

Battle of Red Cliffs took place in 208 AD. Cao Cao, who just unified the north, commanded an army of 200 thousand, claiming to be 800 thousand. He went down the Yangtze River and prepared to "hunt the east of the Yangtze River" with Sun Quan, the Lord of Wu, but was stopped by Sun Liu's 50,000-strong army at Chibi. Because the northern soldiers were unfamiliar with the water war and the plague broke out in the army, they were attacked by Sun Liulian and eventually defeated. This war ended the pace of Cao Wei's unification of the whole country, and also laid the groundwork for the later trend of the three-thirds system.

Although Cao Cao unified the north at that time, the Bashu area was owned by Liu Zhang. Although Liu Biao's son Liu Cong surrendered to Cao Cao, Jingzhou was still largely controlled by Liu Qi and Liu Bei. Without the support of Bashu, Cao Cao was eager to attack Jiangdong, which eventually led to a rout.

3.？ Battle of unifying Wu Dong in the Western Jin Dynasty. (warring sides: western Jin VS Soochow, winner: western Jin)

More than 70 years later in Battle of Red Cliffs, in AD 280, the Emperor Wu of Jin sent Du Yu as the commander-in-chief of the front line, sent 200,000 troops and led the Sixth Route Army to crusade against Wu Dong. This time, Wu Dong was completely defeated and finally went to extinction.

Geographically, Si Mazhao, the father of Sima Yan, Emperor Wu of Jin Dynasty, wiped out the Shu-Han regime as early as AD 263. When the Western Jin Dynasty conquered the State of Wu, the control of Bashu was already in the hands of the Western Jin Dynasty, after years of hard work.

In 276 AD, four years before the general attack on the State of Wu, yang hu, a general, had put forward the general strategic policy of "going downstream and going hand in hand with land and water". In the course of the war, Wang Zhuo, which started from Bashu Waterway, was in full swing along the river, first arrived at Jianye City, and then rushed into Stone City, forcing Sun Hao, the Lord of Wu, to surrender, which played an irreplaceable role.

4.？ The battle of unifying South Chen in Sui Dynasty. (warring sides: sui dynasty VS southern dynasty Chen winner: sui dynasty)

During the Northern and Southern Dynasties, which lasted for nearly 300 years, the North was unable to complete the unified war against the South, mainly because the Southern Dynasties always had control over Bashu. In the Liang Dynasty, due to the outbreak of the Hou Jing Rebellion, the Western Wei regime in the north took the opportunity to seize Chengdu, thus occupying the favorable terrain in the upper reaches of the Yangtze River. By the time of Emperor Wendi of Sui Dynasty, due to the loss of Bashu and Jingxiang, the Southern Chen Dynasty had completely lost the natural barrier of the Yangtze River, and Sui Jun went down the river from Sichuan and Xiangyang, thus destroying the Chen Dynasty.

5. The Battle of Mongolia Destroying the Southern Song Dynasty (warring parties: Mongolia VS Southern Song Dynasty winner: Mongolia)

The process of Mongolia attacking the Southern Song Dynasty is relatively long, but it can be roughly divided into two stages. The primary target of Mongolia's early attack was the Central Plains and Huaihe River Basin, but it met with strong resistance and suffered many failures. Later, the Mongols changed their offensive strategy, targeting Sichuan and Dali, then besieged Jingxiang along the river and finally perished in the Southern Song Dynasty.

It can be seen that Bashu area has a decisive strategic position in the history of China ancient war. It is no exaggeration to say that the North-South unification war was basically won on the basis of occupying Sichuan. The rugged Shu Road, the majestic Jiange, Dujiangyan for the benefit of future generations and the splendid Jinguan City have written one legendary story after another, which has determined the historical trend of China again and again.