In 200 AD, Cao Cao defeated Yuan Shao in the battle of Guandu, and then unified the north, occupying the territories of eight states: You, Ji, Qing, He, Yan, Yu and Xu, forming a pattern of unifying the Central Plains. Then he sent troops to pacify the forces of Wu Huan in Liaodong, basically stabilized the rear area and became an unparalleled man of the hour on the historical stage. But for Cao Cao, who has always had the ambition of "the mountain is not too high, the water is not too deep, the duke of Zhou vomits food, and the world returns to his heart", unifying the north can only be regarded as the first step of the long March. His grand goal is to eliminate all separatist forces and realize the ideal of "one country under the world", so he actively participated in the preparations for the war in the south of the Yangtze River: he built a Xuanwu pool in Yecheng to train the water army, and sent people to Liangzhou to seal Wei Yan for Marten so as not to be threatened by the rear when he went south. After everything was ready, Cao Cao went to the south in full swing. At that time, there were mainly two separatist forces in the south. One is the Sun Quan regime of Wu Dong, which established a third country, six counties in Yangzhou. These places were rich in land and products, and there were few wars at that time. However, the northward migration brought advanced production technology to the local area, so Wudong's economy has developed greatly. Militarily, Sun Quan has tens of thousands of elite soldiers, such as Zhou Yu, Cheng Pu and Huang Gai. Internal unity, coupled with the natural barrier of the Yangtze River, made it the main obstacle for Cao Cao to annex the world. Another big separatist force in the south is Liu Biao in Jingzhou. Basically, he adopted the policy of maintaining the status quo, but he was old and sick, weak, and his sons Liu Qi and Liu Cong were fighting for the right of inheritance, so the regime was not stable. As for Liu Bei, he didn't have his own permanent residence at that time. Liu Bei was originally a descendant of the royal family in the Western Han Dynasty, but the branch relationship was very distant. His father only served as a small palace for county magistrates and state and county officials. When he was young, he "sold shoes and made a seat for his mother", and his family was not rich. Compared with those warlords who rose at the same time, his strength is weak. Therefore, in the melee of warlords, they were repeatedly frustrated and turned to others. In the battle of Guandu, Yuan Shao sent troops to disturb the rear of Cao Jun, and was defeated by Cao Cao, who took refuge in Liu Biao. Liu Biao asked him to lead some troops to Fancheng, hoping to use him to strengthen the defense around Jingzhou, the capital. Unexpectedly, his precious son lived up to expectations and surrendered to Cao Cao without telling Liu Bei, resulting in Liu Beilian's last piece of land being lost. Although Liu Bei has no fixed place to live, his ambition of "reviving the Han Dynasty" has never died out. When he was in Jingzhou, he actively trained the army, recruited talents and prepared to open up a new situation. At that time, many scholars in exile in Jingzhou and local scholars in Jingzhou joined him, and it was at that time that Zhuge Liang, a famous politician, left the mountain at Liu Bei's repeated invitation. Zhuge Liang and Liu Bei formulated a general strategy to seize the world: to unite Sun Quan in the east, to occupy Jingzhou and Yizhou in the west, to win over foreign and Vietnamese minorities in the south, and to resist Cao Cao in the north. According to the plan, Liu Bei brought Jingzhou into his big plan. It is another important obstacle for Cao Cao to annex the world. In July 2008, Cao Cao led the army south, and his first strategic goal was Jingzhou. Jingzhou has always been a battleground for military strategists. If occupied, we can not only control the two lakes, but also attack Wu Dong from the side. To the west, you can capture the rich Yizhou. At the critical moment of the war, Liu Biao, who was as timid as a mouse, died in August. Replacing the second son Bret is even more disappointing. He let Cao Cao's soldiers intimidate him, and without any resistance, he withdrew from Jingzhou. Cao Cao completed the first step of the strategy of going south without bloodshed. After learning the news of Liu Cong's surrender in Fancheng, Liu Bei quickly led the troops to retreat to Jiangling, and ordered Guan Yu to lead the water army to meet at Jiangling via Hanshui River. energy

Liu Bei only took dozens of riders such as Zhuge Liang, Zhang Fei and Zhao Yun to break through. After joining forces with Guan Yu and Liu Qi, he retreated to Fankou on the south bank of the Yangtze River. Successive military victories made Cao Cao triumphant and arrogant, trying to pursue victory and go downstream, occupying the whole area east of the Yangtze River and destroying Sun Quan's power in one fell swoop. Although Jia Xu, an adviser, suggested that he make use of Jingzhou's rich resources, regulate the army and the people, consolidate new land, and then land in Sun Quan with a strong advantage, Cao Cao would not listen. At the moment when the enemy's situation was critical and life and death were uncertain, Sun Quan, at the suggestion of Zhou Yu, a military adviser, agreed to unite with Liu Bei to fight Cao. In A.D. 10, Zhou Yu led his troops along the river to Fankou and joined forces with Liu Bei. Then move on and meet you at Chibi. Frustrated, Cao Jun returned to Jiangbei and settled in Wulin. Across the river from Sun and Liu Lianjun. After losing the first battle, Cao Cao was very angry. He called Jingzhou generals Cai Mao and Zhang _ to the coach's boat and asked, "Why did I lose to Zhou Yu with so many troops?" Cai Mao bowed his head and replied, "Jingzhou Water Army hasn't practiced for a long time. Soldiers in Qingzhou and Xuzhou are not used to water warfare, so their combat effectiveness is not so good. Finally, I will be willing to step up training and let the soldiers in the north learn to fight in water. Please rest assured. " Cao Cao said: "You are all generals of the water army, but you must practice hard and make no mistakes!" The two generals retreated and surrendered to Nuo Nuo. But the training effect of soldiers from the north is not good. When the wind blows, there are waves on the river, and many people get seasick, vomit, can't sleep, can't eat and are exhausted. The soldiers in the dry stockade are not seasick, but the situation is also very bad. That year coincided with the outbreak of winter plague, and many people were sick. These were all in a hurry, so Cao Cao sent people to collect herbs and called ministers to discuss countermeasures. Someone put forward a suggestion: "connect the warships one by one with chains, and then lay boards on them to make a' chained ship'." In this way, no matter how big the wind and waves are, the ship will not shake and the soldiers will not get seasick. "People think it over and over again and think it's a good idea. They all agreed. Cao Cao agreed to have a try first. I tried, and it worked. Fight like a war. It's going well. The people above seem to be on the flat ground, and even horses can get on and off the boat without anyone shouting. So Cao Cao ordered the army blacksmith to build chains, iron rings and nails overnight for the rendezvous of warships.