The relocation of people there now not only hurts the hearts of the locals, but also discourages those who want to return. Cao Cao listened to his advice and did not emigrate. The fugitives who had fled from Tibet before had indeed returned to naturalization.

In the first year of Yankang (220), Cao Cao died, the government and the opposition were in danger, Sima Yi managed the funeral affairs, solemn inside and outside, and returned to Yecheng with Cao Cao's Zi Palace. In the same year, Cao Pi was the throne of Wei, and Sima Yi was awarded the title of Marquis of Hejin Pavilion and became prime minister for a long time. At that time, Sun Quan was leading his army westward. The courtiers believed that Fancheng and Xiangyang lacked food and could not resist the Wu army, so they summoned the guard general Cao Ren back to Wancheng (present-day Wancheng District, Nanyang, Henan). Sima Yi said: "Sun Quan has just defeated Guan Yu, and it is when he wants to get along with Wei State, he must not dare to do it. Xiangyang is an important place for land and water transportation, and it cannot be abandoned. Cao Pi didn't listen to his suggestion and ordered Cao Ren to set fire to the second city. Later, Sun Quan really did not come to invade. Cao Pi regretted it too late.

Auxiliary government quells chaos

In November of the first year of Emperor Wen of Wei (220), Cao Pi ascended the throne and was known as Emperor Wen of Wei in history. After Cao Pi ascended the throne, he appointed Sima Yi as Shangshu, and soon transferred to the overseer, the imperial history Zhongcheng, and the marquis of Anguo. In the second year of the early Huang dynasty (221), he was removed from the post of overseer and promoted to the position of servant and the right servant of Shangshu.

In the fifth year of the early Huang dynasty (224), Cao Pi attacked Wu and watched the army in the river. Sima Yi was ordered to guard Xuchang, and changed the title of Sima Yi to Xiang Xiang, transferred to the army, the holiday, led 5,000 soldiers, and added the matter to the middle and record the book. Sima Yi refused to accept it, and Cao Pi said: "I deal with national affairs day and night, and there is no time to rest. Now I canonize you not to glorify you, but to share your sorrows for me. ”

In the sixth year of the early Huang dynasty (225), Cao Pi once again attacked Wu and ordered Sima Yi to stay in Xudu, pacify the people internally, and provide military funds for the army externally. Before leaving, Cao Pi issued an edict to Sima Yi and said: "I am deeply worried about logistics and internal affairs, so I entrust these important matters to you. Although Cao Shen had many military exploits in history, Xiao He's support in the rear was more important. Is it feasible for you to stay behind now so that I don't have to worry about the west? Later, Cao Pi returned to Kyoto from Guangling (now Guangling District, Yangzhou, Jiangsu), and issued an edict to Sima Yi: "I will use troops to the east, Sun Quan, and you should prime minister the affairs of Luoyang, Kyoto; I am in Luoyang, and you should be the prime minister of the war against Sun Quan. So he ordered Sima Yi to stay in Xuchang.

In May of the seventh year of the early Huang dynasty (226), Cao Pi became seriously ill. When he was dying, he made Sima Yi and Cao Zhen, the general of the Chinese army, Chen Qun, the general of the Zhenjun, and Cao Xiu, the general of the Eastern Expedition, as auxiliary ministers. Cao Pi said to the crown prince Cao: "The three important ministers here, you must not doubt them. Cao ascended the throne and changed the title of Sima Yi to the Marquis of Wuyang. When Sun Quan learned of the death of Emperor Wen of Wei, he sent troops to attack Wei in August. He ordered Zhuge Jin and Zhang Babing to attack Xiangyang in two ways, and personally led the army to attack Jiangxia County (Zhishiyang County, that is, southwest of present-day Huangpi, Wuhan). Sima Yi repelled Sun Quan, defeated Zhuge Jin, and beheaded Zhang Ba, beheading more than a thousand ranks. In December, Sima Yi was promoted to hussar general.

Capture Mengda

In June of the first year of Taihe (227), Emperor Cao of Wei Ming ordered Sima Yi to be stationed in Wancheng and supervise the military forces of Jing and Henan. When Shu surrendered Meng Da to Wei, Wei treated him very kindly, and Sima Yi thought that his words and deeds were clever and could not be trusted. But Cao did not listen, and appointed Meng Daling Xincheng (now Fang County, Hubei) as the Taishou. After Cao Pi's death, Meng Da fell out of favor, and Zhuge Liang, the prime minister of Shu, secretly corresponded with him and plotted to betray Wei. Zhuge Liang was afraid that his words and deeds would be capricious, and wanted to urge him to rebel quickly, knowing that Wei Xing was too protective of Shen Yi and had a conflict with him, so he sent Guo Mo to Shen Yi to deceive him, intending to leak his matter. When Meng Da heard of this, he prepared to raise troops immediately. After Shen Yi told Sima Yi about the matter, Sima Yi was afraid that he would suddenly attack, so he sent him a letter to comfort him. Meng Da was overjoyed, but hesitated. Sima Yi secretly led the army to discuss, and the generals saw the handover between Meng Da and Wu Shu, and persuaded Sima Yi to watch first and then move. Sima Yi said: "Meng Da has no faith, now is the time for him to hesitate, we should take advantage of his lack of decision and pacify him in time." Sima Yi personally led the army to attack Meng Da day and night, and arrived at the city of Xincheng in eight days. Wu and Shu sent reinforcements to rescue Meng Da, but they were stopped by Sima Yi's troops in Anqiao, Mulansai and other places in Xicheng.

Sima Yi fought against Mengda

Previously, Zhuge Liang had warned Meng Da to step up precautions, and Meng Da wrote to Zhuge Liang that "Wancheng and Luoyang are eight hundred miles apart, one thousand two hundred miles away from me, and the table is given to the Son of Heaven, and the round trip takes less than a month, and at that time my city has been repaired, and all the armies are ready." The terrain where I am stationed is very dangerous, Sima Yi will not come in person, and the other departments will not be troubled in the future." And Sima Yi cut first and then played, and the troops came to the city on the eighth day, Meng Da wrote to Zhuge Liang again, exclaiming: "I want to do something, and Sima Yi will come to the city on the eighth day, how fast!" Shangyong City (now southwest of Zhushan County, Hubei) was surrounded by water on three sides, and Meng Da set up a wooden fence outside the city to strengthen the city defense. Sima Yi waved his army across the water, destroyed its wooden fence, and approached the city. In the first month of the second year of Taihe (228), Sima Yi's soldiers attacked the city in eight ways, and only 16 days later, Meng Da's nephew Deng Xian and his general Li Fu surrendered. The Wei army entered the city, captured Meng Da, passed the first Beijing division, and captured more than 10,000 people. Sima Yi returned to the army and was still stationed in Wancheng, rewarding and persuading farmers and prohibiting waste. The people of the south are happy and convinced.

At first, Shen Yijiu was in Weixing County, tyrannical power, and engraved a seal letter in the name of the emperor without authorization, and granted it privately. After Meng Da was killed, Shen Yi had doubts. At that time, the county guards saw that Sima Yi had defeated the enemy, and they all congratulated him. Sima Yi let it go, and let people hint to Shen Yi. Shen Yi had no choice but to come to congratulate. Sima Yi took the opportunity to arrest him and send him to Beijing. Sima Yi also moved more than 7,000 families of Meng Da Yu to Youzhou. Soon, Shu generals Yao Jing and Zheng He led more than 7,000 of their subordinates to surrender. At that time, the border county was newly attached, and the household registration was false. The imperial court wanted to verify it, so it asked Sima Yi to go to Beijing and ask for his opinion. Sima Yi believed: "The traitor restricts his subordinates with strict laws, so he is abandoned by his subordinates. Treat them with leniency, and they will be happy."

Cao asked him again that Wu and Shu should be defeated, where should they start first? Sima Yi replied: "Wu Guo thinks that our northern soldiers are not used to water warfare, so they dare to scatter in Dongguan. As long as you attack the enemy army, you must choke the throat of the enemy army and hit their heart, and Xiakou and Dongguan are the heart throats of the Wu army. If the army attacked Anhui City on land, because Sun Quan's soldiers and horses went east, he sent a naval division to attack Xiakou and take advantage of his weakness to attack it, and he would definitely be able to break the Wu army. Cao was deeply impressed with his opinion, and once again ordered Sima Yi to prepare for war in Wancheng. In August, the great Sima Cao Xiu did not follow the plan, and went down to Anhui City to go deep into the enemy territory to meet the Wu general Zhou Yi, who had surrendered fraudulently, and was ambushed by Lu Xun in Shiting, defeated, and Cao Xiu died of illness.