The Longzhong Plan (隆中對) is the name given to a strategic plan given by the third century Chinese tactician and administrator Zhuge Liang. It formed the basis for the grand plan of the warlord Liu Bei and later the Three Kingdoms state of Shu. In essence it envisaged the securing of a viable regional base in southern China, and then a two-pronged attack to conquer the north. Though the plan was directed at the powerful Wei state, the ultimate aim of reunifying the empire of the fallen Han Dynasty necessitated the eventual destruction of Sun Quan's regime of Wu in the east.
Zhuge Liang joined Liu Bei as moushi (謀士), an advisor on strategic matters, in 207. According to Sanguo Zhi, it was at this time that he outlined the Longzhong Plan. The plan envisaged that Liu Bei would take over Jing and Yi provinces, both of which were ruled by relative incompetents. The Longzhong Plan noted that Cao Cao controlled the North China Plain, which was key to mastery of China, and that Sun Quan held the lower Yangtze River region, known as "Jiangdong". In view of this, a move to occupy Jing and Yi was vital for success. The essential outlines of the plan held remarkable foresight in envisaging the tripartite division of China. The other crucial aspect of the plan was the proposal for forming an alliance with Sun Quan in order to deter and resist the more powerful and intimidating Cao Cao. Other minor aspects included the institution of economic, legal and administrative reforms as well as developing cordial relations with the non-Han people located in the west and south. Such a policy would reduce resistance and increase much-needed manpower and economic resources. The culminating clause was a two-pronged northern campaign which would end in the seizure of the North China Plain and the reestablishment of the Han court.
One advance would be from Yi in the west, north through the Qin Mountains, which debouches into the Wei River valley and achieving a strategic position in the west from which to dominate the great bend of the Yellow River and the Guanzhong region. The second advance would be from Jing north toward the political centre of Luoyang and the surrounding plains. Such a campaign would presumably occur at an opportune moment of destabilisation of Wei but that moment was not specified. Nor was the role of Sun Quan in the offensives identified; though it would be assumed that he would tie down at least some of Cao Cao's forces.
From 215 Liu Bei controlled both Jing and Yi provinces. In 219, he won a decisive victory over Cao Cao and occupied Hanzhong. That autumn, his commander in Jing, Guan Yu, struck north against Cao Cao's positions on the Han River. This offensive may have been part of the planned two-pronged attack. For the first few months, Guan Yu's attack was remarkably successful and Cao Cao even considered evacuating the capital Xuchang. At this point, however, Sun Quan took the opportunity to launch a surprise attack and rapidly seized Jing Province. Liu Bei tried unsuccessfully to recapture Jing in 223 (see Battle of Xiaoting), and died shortly thereafter. Even with the loss of Jing province, Zhuge Liang may have attempted to carry out a modified version of the Longzhong Plan in the form of the Northern Expeditions, although it is arguable that those campaigns had different tactical and strategic goals.
The great Qing Dynasty scholar Wang Fuzhi was critical of the strategic goal of the Longzhong Plan because the two-pronged offensive that was intrinsic to the plan did not make a distinction as to which prong was the decoy and which was the main force. He alludes to the plan as being without any subtlety: such as using the stratagem "make a sound in the east but strike in the west" (聲東擊西 shēng dōng jī xī). Nor did it incorporate any hint of the interplay between zheng (正)and qi (奇) - the orthodox, apparent and overt military operation, and its opposite, a surprise, covert, or unexpected military action which brings about victory for a weaker force. Wang Fuzhi notes that one who seeks to seize the empire from a comparatively weak position must be flexible in strategic planning in order to grasp the opportunity to use qi to obtain victory.
Others charge that the political goal of the Longzhong Plan was flawed because the restoration of the Han Dynasty was unrealistic. The Wei government, considered by Zhuge Liang to be illegal, had effectively dealt with economic and political issues and had gained the support of the people. The military historians at the Military Science Academy in Beijing view Zhuge Liang's political goal as inappropriate and unrealistic even in 207 when the plan was formulated and totally irrelevant by the time of the Northern Expeditions. The idea of seizing Jing Province in the Longzhong Plan was a flawed concept because Sun Quan would never accept Liu Bei in control of this critical area, crucial for the security of his base in Jiangdong. In essence, Zhuge Liang is charged with failing to make an objective analysis of the political situation in 207.