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.

Empress Zhang had died in 237, and later in that year year, Liu Shan had taken her younger sister as a consort; in 238, he creates her empress.

Her title remains the same as her sister’s, Empress Zhang.

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.

The arrival of Germanic-speaking invaders along the coast of the Black Sea is generally explained as a gradual migration of the Goths from what is now Poland to Ukraine, reflecting the tradition of Jordanes and old songs.

The Goths—Germans coming from what is now Sweden—will be followed by the Vandals, the Burgundians, and the Gepidae.

The aftereffect of their march to the southeast, toward the Black Sea, had been to push the Marcomanni, the Quadi, and the Sarmatians onto the Roman limes in Marcus Aurelius' time.

Their presence is brusquely revealed to the civilized Greco-Roman world when they attack the Greek towns on the Black Sea about 238.

The Goths, in the first attested incursion into Thrace, are mentioned as Boranoi by Zosimus, writing at the turn of the sixth century, and as Boradoi by Gregory Thaumaturgus.

The first incursion of the Roman Empire that can be attributed to Goths is the sack of Histria in 238.

The town suffers serious destruction from which it will never recover.

The main theory is that it is destroyed by Gothic invasion; another theory presumes that the town was destroyed in an earthquake.

Maximinus spends most of his reign fighting invading tribes along the Danube and the Rhine.

The numerous milestones displaying his name attest to his energetic reconstructions of the roads in these regions.

Hatra defeats the Iranians in 238 at the battle of Shahrazoor, a plain between Sulaymaniyah and Derbendixan, situated in the southeastern part of Iraqi Kurdistan.

A treasury official's extortions through false judgments in corrupt courts against some local landowners ignite a full-scale revolt early in 238 in the province of Africa.

The landowners, who are mostly young and wealthy, arm their clients and their agricultural workers and enter Thysdrus (modern El Djem), where they murder the offending official and his bodyguards and proclaim the aged governor of the province, Marcus Antonius Gordianus Sempronianus (Gordian I), and his son, Gordian II, as co-emperors.

The Senate in Rome switches allegiance, gives both Gordian and Gordian II the title of Augustus, and sets about rousing the provinces in support of the pair.

Maximinus, wintering at Sirmium, immediately assembles his army and advances on Rome, the Pannonian legions leading the way.