Referring to the chaotic era of the Three Kingdoms, "Zhuge Liang" spent his life to open up the territory of Shu Han and conquer the north, which can be called the optimus pillar of Liu Bei's jiangshan; especially after Liu Bei died in the White Emperor City, the family foundation that Shu Han had saved for many years was almost lost, at this time Zhuge Liang officially took over Shu Han with full authority and began a political career of "grasping the military and government with one hand". At this time, another important figure also appeared, that is, the important general "Wei Yan" in the late Shu Han Dynasty; speaking of his people, there was also a "famous plan for thousands of years" - the Meridian Valley Conspiracy.
The simple explanation of the "Meridian Valley Conspiracy" is that "Wei Yan" led his own or 5,000 or 10,000 soldiers and horses to enter the army separately from Zhuge Liang, and "Wei Yan" copied the "Meridian Valley" to take Chang'an directly, and then stuck to Chang'an and Tongguan; at the same time, Zhuge Liang 's "Oblique Valley" entered the army, and the two armies met at Tongguan, so that "Guanzhong" could be determined. At first glance, this plan is quite a skill of war, if you get the important town of "Chang'an", Shu Han will not only get the land of Guanzhong, but even directly into the hinterland of Cao Wei; if this plan is successful, although Cao Wei will not be destroyed in an instant, it will certainly be chaotic in the world, and then Zhuge Liang seems to be able to take the northern cities in one fell swoop.
However, the "Meridian Valley Conspiracy" was still rejected by Kong Ming, and for this reason "Wei Yan" complained everywhere, saying that "Zhuge Liang did not understand soldiers"; even in later generations, there were many voices supporting "Wei Yan", saying that not using the "Meridian Valley Strategy" was Zhuge Liang's biggest failure, and even upgraded to the height of Kong Ming's jealousy. Is it really Zhuge Liang who "doesn't understand soldiers"? Or is Kong Ming really a "villain" who is jealous of Xian's ability? Later generations continued to be controversial about this, and even left a pause of "Zhuge Liang as an unknown soldier" to satirize those who were arrogant and arrogant and self-righteous; in fact, Zhuge Liang did not use the "Meridian Valley Conspiracy" not to have an opinion on Wei Yan, but to protect him.
"Shu Han is weak" This is an indisputable fact, and more than 10,000 elites have almost become "heart meat" for Zhuge Liang. Imagine that "Wei Yan" went out of the Meridian Valley to attack Chang'an, if it succeeded, the soldiers and horses from all over Cao Wei would definitely rush to the rescue, and 10,000 people could hold it? If "Wei Yan" could not successfully take "Chang'an" out of the Meridian Valley, it would be equivalent to going deep alone, and the consequences were self-evident. In this way, no matter whether "Wei Yan" could capture Chang'an or not, zhuge Liang's speed of coming out of the valley would certainly not be able to rescue in time; failure to rescue in time meant that "Wei Yan" was facing a life and death choice. Out of the overall view, after all, at that time, shu Han was already incompetent, and "Wei Yan" was the only remaining famous general of the Three Kingdoms; although there were flaws, Zhuge Liang was not willing to waste the "Wei Yan" who was still talented.
This is only one thing, and the second is more important. As the old saying goes, "Soldiers, tricks", a qualified military expert is not limited to "marching and fighting", but also considers the general situation of the world at that time. I think that "Guan Yu" took the lead in the Northern Expedition, and all the way to the ground, encircling Cao Ren, chopping Pound, capturing Yu Ban, flooding the Seventh Army, and even forcing Cao Cao to have the idea of moving the capital for a while; it is reasonable to say that this speed is fast enough, is this the situation a good situation? However, Eastern Wu stabbed Guan Yu in the back at this time, which was nominally because Eastern Wu wanted to retake "Jingzhou", but in fact did not allow Shu Han to dominate.
The so-called "Sun Liu Alliance" is, in the final analysis, just a formal joint resistance to Cao, but the ultimate goal of both "Liu Bei" and "Sun Quan" is to unify the Central Plains by themselves, and maybe even want to be "emperor". Since "Sun Quan" also wanted to be emperor, how could he watch the Shu Han Festival triumph and do nothing himself? Moreover, once the Shu Han dynasty destroyed Cao Wei, the next one was bound to use troops against "Eastern Wu", and from this point of view, Sun Quan did not allow "Guan Yu" to succeed in the Northern Expedition.
Saying "Guan Yu" is actually to explain the "Meridian Valley Conspiracy", Zhuge Liang's Northern Expedition is actually the same as the situation faced by the "Battle of Xiangfan" in that year; after all, Eastern Wu had pinned down a large number of Cao Wei's troops in the "Hemi" area of the Eastern Front, and at this time Zhuge Liang could use troops to compete with Cao Wei's troops, and perhaps have some advantages in other aspects. If Zhuge Liang had adopted Wei Yan's so-called "Meridian Valley Conspiracy" at this time, not to mention whether it was successful or not, the mere act of entering the hinterland of Cao Wei was bound to arouse the suspicion of Eastern Wu; and if "Wei Yan" was lucky enough to succeed, then Eastern Wu was likely to stage the "stabbing knife" behind his back again.
If in this case, Eastern Wu once again betrayed the alliance and formed an alliance with Cao Wei, then part of Cao Wei's eastern front could be transferred to the southwest to fight against Zhuge Liang and "Wei Yan"; at that time, not only did "Wei Yan" fail ironcladally, but even whether Zhuge Liang could retreat with his whole body was a problem. This is not the worst situation, what if the "Eastern Wu Betrayal Alliance" and join forces with Cao Wei will stage another situation in which "Lü Meng" sent troops to cut down Shu? At this time, Zhuge Liang's army was in Xiegu and Wei Yan was in Chang'an, and it would definitely be too late to return to the army to resist "Eastern Wu". At the same time, Cao Wei re-attacked, and at this time Zhuge Liang was faced with a double-line attack of "Cao Wei" in the north and "Eastern Wu" in the south; at that time, even if Kong Ming had the ability to reach the heavens, it would be difficult to resist, and even the "Shu Han regime" would be destroyed.
Therefore, Zhuge Liang knew very well that the more dangerous the use of troops, the higher the dependence on Eastern Wu; as an outstanding "military expert", Kong Ming first considered not the question of whether the "Meridian Valley Conspiracy" could succeed, but the first consideration of whether Eastern Wu would pose a threat. At that time, Kong Ming had already had the strategy of "Longzhong confrontation", and if he wanted to unify the Central Plains, the first thing to do was to "cross the Jingyi and marry Sun Quan"; at this time, Zhuge Liang had lost the strategic point of "Jingzhou", but his dependence on "Eastern Wu" had not diminished in the slightest.
Shu Han only had a barren "Yizhou" and a part of the surrounding area that was equally barren, and such capital could not fight a war of attrition with Cao Wei at all; however, the "three-legged standing" pattern that had been formed so hard was unbreakable because all three parties had their own needs. This prompted Zhuge Liang to take into account the "general trend of the world" when using troops, and even to control the speed of the march within a certain range; if the speed was too fast, the Eastern Wu would betray the alliance, and if the speed was too slow, it would not be worth the loss. This was also one of the main reasons why Zhuge Liang either had poor grain and grass in several Northern Expeditions, or immediately withdrew from the army when there was a slight disadvantage; it was a pity that Wei Yan could only be a "general" and could not understand the suffering of "Shuai".
Therefore, whether Wei Yan's "Meridian Valley Conspiracy" can be successful in the end, Zhuge Liang will reject it from a macro perspective