Yang Yi, the Imperial Secretariat of the state of Shu Han, has participated in the Northern Expeditions of Shu under the command of the strategist Zhuge Liang.

He and Wei Yan do not get along well, and it is only the command of Zhuge Liang that keeps them from fighting one another outright.

Zhuge Liang has launched a series of six invasions on Cao Wei between 228 and 234, but has failed each time due to lack of supplies or the incompetence of his officers.

In the spring of 234, Zhuge Liang leads one hundred thousand troops through Xiagu Pass after three years of preparation since his last Northern Expedition.

At the same time, Zhuge Liang sends an emissary to Shu Han's ally state, Eastern Wu, hoping that Wu will attack Cao Wei concurrently.

In April, Shu forces reach the Wuzhang Plains near the Wei River and make camp there.

The Cao Wei commander, Sima Yi, is well-prepared with a two hundred thousand-strong army, which holds a fortified position on the southern bank of the Wei River.

Guo Huai suggests that Sima Yi form a position in the northern part of the Plains, since Zhuge Liang will likely strike there.

Sima Yi agrees, and sends Guo Huai to set camp there.

Shu forces attack the Wei camp there while it is being built, but Guo Huai is able to hold them off.

Sima Yi will not engage the Shu forces, instead trying to make the enemy retreat through attrition.

Zhuge Liang understands the problem, and implements the tuntian system to sustain his troops.

While the tuntian system is made famous by Cao Cao's administration, Cao's writings show that the system had been instituted as early as the Western Han dynasty, during the reign of Emperor Wu, where soldiers on distant expeditions were set to work converting and farming the conquered land, both to provide food for the army and to convert the region into one based around agriculture—in effect, an economic conquest.

After the death of Emperor Wu, however, the system was only used sporadically and therefore less effectively.

The Shu army awaits an agreed offensive by Wu for the moment to strike.

However, Sun Quan's armies in the Huai River region are defeated by forces led by the Wei emperor, Cao Rui, and succumb to an endemic disease.

Thus the stalemate remains in place and continues for hundreds of days.

Shu forces try to engage the Wei forces several times, but Sima Yi remains firmly in camp and refuses to engage the enemy.

In an attempt to provoke Sima Yi to attack him, Zhuge Liang sends women's clothing to Sima, suggesting that Sima should be a woman since he does not dare to attack him.

Sima Yi's subordinates are enraged by the insult, but Sima himself remains calm.

To appease his men, Sima Yi asks Cao Rui for permission to engage the enemy.

Cao Rui understands the situation and sends minister Xin Pi to persuade the Wei army to be patient.

In another attempt to force Sima Yi to go to battle, Zhuge Liang sends an emissary to urge Sima to fight him.

However, Sima Yi refuses to discuss military issues with the messenger, and instead inquires about Zhuge Liang's daily tasks.

The emissary replies that Zhuge Liang has been personally overseeing all affairs in the army, ranging from strategic planning to his men's daily meals, and that Zhuge himself has not been eating and sleeping well.

Sima Yi later tells an aide that Zhuge Liang will not last long.

In August, Zhuge Liang falls ill due to exhaustion, and his condition worsens daily.

News reaches the Shu emperor, Liu Shan, who sends minister Li Fu to ask Zhuge Liang about future plans for Shu.

Zhuge Liang replies that Jiang Wan can succeed him, and Fei Yi can succeed Jiang.

When Li Fu asks again about Fei Yi's successor, Zhuge Liang falls silent.

Li Fu then returns to the capital Chengdu.

Zhuge Liang also gives instructions on how the Shu forces should withdraw back to Hanzhong: Yang Yi and Fei Yi will lead the army while Jiang Wei and Wei Yan will lead a force to defend the rear; if Wei Yan disobeys orders, the army will proceed on without him.

Zhuge Liang eventually dies at the age of 53 in the early autumn of 234.

Yang Yi and Wei Yan argue about whether to follow Zhuge's orders to retreat.

Their disagreement finally breaks out into a full-fledged battle, which Yang Yi eventually wins.

He also slays Wei Yan's entire family shortly after.

Zhuge Liang grows seriously ill while on his final campaign against Wei in 234.

Liu Shan, hearing of Zhuge's illness, sends his secretary Li Fu to the front line to visit Zhuge Liang and to request Zhuge to leave instructions on important state matters.

Among other things, Zhuge recommends that Jiang Wan succeed him, and that Fei Yi succeed Jiang Wan.

Zhuge Liang refused to answer Li Fu's next question—who should succeed Fei Yi.

Zhuge Liang dies soon thereafter.

Liu Shan follows Zhuge's instructions and installs Jiang Wan as the new regent, but Jiang is more interested in domestic affairs than military expansion.

Thus the death of Zhuge Liang ends a huge strategic threat to Cao Wei and the Wei court soon begins development of ambitious public works.

Sima Yi's success and subsequent rise in prominence paves the way for his grandson Sima Yan's founding of the Jin dynasty, which will eventually bring an end to the Three Kingdoms period.

Cao Rui had commenced large-scale palace and temple-building projects almost immediately after ascending the throne.

Part of it was to be expected—the Luoyang palaces had been remnants of the ones not destroyed by Dong Zhuo, and the temples were needed for the cults of his ancestors.

However, he has gone beyond the minimally required constructions, and continues to build temples and palaces throughout his reign, severely draining the imperial treasury.

While he occasionally halts projects at the officials' behest, the projects restart after brief breaks.

He not only builds palaces in Luoyang, but also builds a palace in Xuchang.

In 237, he further moves many of the magnificent statues and monuments that had been commissioned by Emperor Wu of Han from Chang'an to Luoyang, at great expenses and the cost of many lives.

He further builds gigantic bronze statues of his own and places them on a man-made hill inside his palace, surrounded by rare trees and plants and populated by rare animals.

Cao Rui is also increasing his collection of women, as his concubines and ladies-in-waiting number in the thousands.

His palace-building projects might have been with intent to house them.

In 237, he even orders that beautiful married women all be formally seized unless their husbands are able to ransom them, and that they will be married to soldiers instead—but that the most beautiful among them will become his concubines.

Despite some officials' protestations, this decree is apparently carried out, much to the distress of his people.

Despite his harem, however, Cao Rui is without any son who survives infancy.

He had adopted two sons to be his own—Cao Fang and Cao Xun, whom he had created princes in 235.

(It is usually accepted that they were sons of his cousins, although the exact parentage is not clear.)

In 237, Cao Rui takes the unprecedented (and unrepeated in Chinese history) action of setting his own temple name of Liezu and ordering that his temple never be torn down in the future.

(Based on Confucian regulations, except for the founder of the dynasty, rulers' temples are destroyed after six generations.)

He carries out these actions apparently in apprehension that he will be given an unflattering temple name (or none at all) and that his temple will eventually be destroyed, due to his lack of biological issue and unclear origin.

By 237, Cao Rui's favorite is no longer Empress Mao, but Consort Guo.

In this year, when Cao Rui is attending a feast hosted by Consort Guo, Consort Guo requests that Empress Mao be invited to join as well, but Cao Rui refuses and further orders that no news about the feast be given to Empress Mao.

However, the news leaks, and Empress Mao talks about the feast with him anyway.

He becomes exceedingly angry, and kills a number of his attendants whom he suspected of leaking the news to Empress Mao, and, inexplicably, orders Empress Mao to commit suicide, even though she is still buried with honors due an empress, and her family remains honored.

Cao Rui sends Sima Yi with forty thousand men to attack Liaodong the following year.

Upon hearing this, Gongsun again requests aid from Eastern Wu.

Sun, angry at Gongsun's previous betrayal, pretends to agree, but does not send Gongsun any actual help.

Although Sima's expeditionary force is also initially halted by torrential rains as had been that of Guanqiu, Sima waits out the rains and eventually surrounds Gongsun's capital of Xiangping (in modern Liaoyang, Liaoning), starving Gongsun's troops.

Xiangping falls after nearly three months of siege; Gongsun flees, but is captured and executed by Sima.

Liaodong becomes part of Cao Wei's domain.

Gongsun Yuan is under attack by Wei's general Sima Yi in 238.

Sun Quan, despite his prior rage against Gongsun, correctly judges the situation as one where he might be able to take advantage if Sima Yi were initially unsuccessful, and does not immediately refuse Gongsun's request for help.

However, as Sima Yi is able to conquer Gongsun Yuan quickly, Sun Quan never launches the major attack that he had considered were Sima to have gotten stuck in a stalemate with Gongsun.

In this year, he also recognizes the manner in which his head secretary Lü Yi had been falsely accusing his officials, and has Lü executed; he then further confirms his trust in the high level officials by personally writing an emotional letter to Zhuge Jin, Bu Zhi, Zhu Ran, and Lü Dai, blaming himself for the recent problems with his administration while urging them to speak out honestly whenever they see faults in him.

Cao Rui grows ill in 238.

He creates Consort Guo empress in preparation of allowing her to become empress dowager after his death.

He initially wants to entrust his adopted son, Cao Fang, the Prince of Qi, to his uncle Cao Yu, to serve as the lead regent, along with Xiahou Xian, Cao Shuang, Cao Zhao, and Qin Lang.

However, his trusted officials Liu Fang and Sun Zi are on unfriendly terms with Xiahou and Cao Zhao and are apprehensive about their becoming regents; they manage to persuade him to make Cao Shuang (with whom they are friendly) and Sima Yi regents instead.

Cao Yu, Cao Zhao, and Qin are excluded from the regency.

Cao Shuang and Sima Yi had shared power initially, but Cao Shuang had quickly employed a number of political maneuvers to honor Sima with honorific titles, including Grand Tutor, while stripping his actual power.

Cao Shuang then makes all important decisions and stops consulting Sima.

Quickly, Cao's associates, including Deng Yang, Li Sheng, He Yan, and Ding Mi, who are known for their talents but lack wisdom, all become powerful, and they exclude from positions of power other officials who will not associate with them.

Sima is still given military authority (including command in repelling a major Eastern Wu attack in 241), but no real authority on governance.

Cao Rui creates the seven-year-old Cao Fang crown prince in the spring of 239, and dies the same day of this creation.

Cao Fang succeeds him as emperor.

Sun Quan appoints his son Sun He, born to Consort Wang, crown prince in 242.

However, he also favors another son by Consort Wang, Sun Ba, the Prince of Lu, and permits Sun Ba to have the same staffing level as the crown prince—a move to which a number of officials object, as encouraging Sun Ba to compete with Sun He, but Sun Quan does not listen to them.

Sun Quan launches the last major assault of his reign against Wei in 241, in light of Cao Rui's death in 239, but he rejects a strategy offered by Yin Zha to attack Wei in a coordinated effort with Shu on four different fronts, and the campaign ends in failure.

The death of the crown prince Sun Deng later in 241 leaves open the issue of succession and appears to mark the start of a precipitous decline in Sun Quan's mental health.