After Liu Bei's death, Zhuge Liang judged the situation and continued to pursue the basic national policy of uniting Wu against Cao, repeatedly taking the initiative to attack Cao Wei and northern expeditions to the Central Plains, trying to realize Liu Bei's last wishes, and reviving the Han Dynasty in the old capital, known as the Battle of "Six Out of Qishan". Zhuge Liang's military talent and loyalty to the State of Shu certainly could not be denied, but as far as the objective situation at that time was concerned, the comprehensive national strength of the State of Shu was far inferior to that of the State of Wei, and it was completely impossible to eliminate the State of Wei, so it was also doomed that Zhuge Liang's Northern Expedition would not have an ideal result.
In the twelfth year of Jianxing of the Shu Han Dynasty (234), Zhuge Liang, who was already 54 years old, once again mobilized soldiers and horses and personally led troops to attack Cao Wei. According to his prior plan, the State of Shu first made an agreement with Sun Quan of the State of Wu, and at the same time attacked the State of Wei, hoping to put the State of Wei in the predicament of being attacked by the enemy on its back. Emperor Cao Rui of Wei was a young and promising emperor. He immediately made a decision, dispatched the veteran general Sima Yi to send troops to resist Zhuge Liang, and he personally marched south to defend Against Sun Quan, and took the lead in repelling Sun Quan's attack at Hefei New City.
Zhuge Liang's lone palm was difficult to sound, but the arrow had to be fired on the string, so he had to go deeper and deeper through the slanted valley to Wuzhangyuan on the south bank of the Weishui River in the Guanzhong Plain. Sima Yi led a large army to arrive almost at the same time, and immediately set up camp to confront Zhuge Liang. Sima Yi, an old and cunning man, discovered one of Zhuge Liang's fatal weaknesses: the supply of logistical grain and grain was extremely difficult, and it was impossible to fight a protracted war.
The grain and grass needed by Zhuge Liang's army, starting from Hanzhong, required a long journey of more than 470 miles to reach Guanzhong, and most of the roads on the way were bumpy and difficult Qinling Mountain Roads, whether it was horse and animal power or people pulling shoulders, or wooden cattle and horses, the march was extremely slow and difficult. Therefore, every time Zhuge Liang sent troops to the Northern Expedition to Cao Wei, he was eager to find the main force of the State of Wei to make a quick decision. Once caught in a protracted stalemate, the situation of the Shu army would be extremely passive.
Sima Yi thought that he had seized Zhuge Liang's "seven inches", and in the previous few encounters, he repeatedly sacrificed this trick, deep ditches and high barriers, strong walls and cleared the wilderness, fought a protracted battle, and repeatedly made Zhuge Liang fruitless. This time, he did the same, repeated the old trick, and wanted to use a protracted battle to exhaust the food and grass of the Shu army and make it retreat in spite of difficulties.
But Zhuge Liang was confident this time. Instead of relying on the rear to transport military food unchanged, he took two countermeasures. The first is to mobilize the army to expand the tun fields along the Weishui river, and strive to do their own work to provide enough food and clothing, and strive to get rid of the dilemma of relying on the rear to transport grain. At the same time, Zhuge Liang also used a killer move: he planned to avoid Sima Yi's frontal obstruction and send troops to capture northern yuan.
Beiyuan was located on the main road from Guanzhong to Longxi, and Zhuge Liang's wishful thinking was to seize The Northern Plains and cut off the Wei state's connection to Longxi, and then he plotted against the Hu people and nomadic tribes living in Longxi to send troops together to invade Guanzhong from the northwest, making the Wei state difficult to care about.
Who would have expected that Sima Yi had a high-ranking man under him: the military general Guo Huai. Guo Huai had been fighting with Zhuge Liang for many years and had rich experience, and he saw through Zhuge Liang's plan and immediately suggested to Sima Yi that "if Liang crosses Wei to ascend to the plains, even the soldiers on the North Mountain, isolate the Long Dao, shake the people and Yi, this is not the interest of the state", Sima Yi suddenly realized, and hurriedly sent troops to occupy the Northern Plains. The Wei soldiers had just arrived in The Northern Plains and were digging trenches, when the Shu army did arrive, only to be repulsed by the prepared Wei army.
Zhuge Liang was unable to make a plan and another plan, he adopted the strategy of attacking the west from the east, ostensibly "marching westward with a strong army, wanting to attack the western siege", marching to the western siege of the military town, but secretly sending elite troops to attack yangsui, a major town in the northwest of the Wei state. Who knows, Guo Huai's eyes were like a torch, once again recognized his mind, "made the officers and soldiers respond to it again", strengthened the Yang Sui guard, Zhuge Liang's surprise soldiers arrived, touched a hard nail again, and returned without success.
At this point, Zhuge Liang had been completely exhausted, and every time he had a brilliant plan, he was recognized by Guo Huai, who expected the enemy to defeat the enemy first and then to the rear, making Zhuge Liang completely passive, and the last Northern Expedition seemed to end in defeat again. Zhuge Liang had already accumulated exhaustion and exhausted, and had been repeatedly thwarted by Guo Huai's brilliant plan, and he could no longer withstand such a blow, so he fell ill and died of Huangquan.
It can be seen from this that Guo Huai is the real murderer of Zhuge Liang. It is said that Sima Yi died in Wuzhang's original qi, but the real history is not so, and Sima Yi has carried the black cauldron in vain for more than a thousand years.
Reference: Romance of the Three Kingdoms