The kingdom of Wèi had conquered Shu Han in 263-64.

Shortly afterwards, in 265, the Wèi dynasty had been overthrown by its last Imperial Secretariat, Sima Yan, grandson of Sima Yi, who founds China’s Western Jin dynasty.

Ruling as Wu Di (Emperor Wu), he has brought a semblance of unity to China.

The persistent Plague of Cyprian, which has ravaged and greatly weakened the Roman Empire for the past fifteen years, finally abates in 265, although intermittent outbreaks will continue through 270.

Historian William McNeill will assert that the earlier Antonine Plague (166–80) and the Plague of Cyprian were outbreaks of two different diseases, one of smallpox and one of measles, although not necessarily in that order.

The severe devastation to the European population from the two plagues may indicate that people had no previous exposure—or immunity—to either disease.

The modern consensus, however, is that both outbreaks were of smallpox. (D. Ch. Stathakopoulos Famine and Pestilence in the late Roman and early Byzantine Empire (2007) 95).

This latter view seems like to be correct given that molecular estimates have placed the evolution of measles after 500 CE. (Furuse, Y.; Suzuki, A.; Oshitani, H. (2010). "Origin of measles virus: Divergence from rinderpest virus between the 11th and 12th centuries". Virology Journal 7: 52.)

Gallienus, breaking with a tradition of some seven centuries, transfers the command of the Roman armies from the senators to professional equestrian officers, thereby sharply reducing civilian control over the military.

At the same time, he expands the role of the cavalry in warfare by creating a mobile cavalry reserve (which is to become the nucleus of the field army of the later empire).

Manius Acilius Aureolus, a Roman cavalry commander under Gallienus, had in 261 defeated in Thrace the army of the usurpers Macrianus Major and Macrianus Minor, who had rebelled against Gallienus.

He is sent in 265, to dispose of the rebellion of Postumus but his carelessness allows the usurper to flee.

Zosimus reports that Aureolus and other two officers conspired against Gallienus, but that all of them were punished and submitted, except Aureolus, who retained his anger against the emperor.

Gallienus, after his failed attempt at defeating Postumus, is occupied with crises in the rest of his empire and will never challenge Postumus again.

Jin, having newly established itself as the successor to Eastern Wu's archenemy Cao Wei after its first emperor, Emperor Wu (Sima Yan) usurped the Cao Wei throne, seeks in 266 to establish peace with Eastern Wu.

Sun Hao instead considers attacking Jin, and while he does not do so at this point, he does not establish peace with Jin.

Also in 266, commoners in modern Zhejiang, unable to withstand Sun Hao's heavy levies (to support his luxuries), rebel and kidnap Sun Hao's brother Sun Qian as a figurehead.

They reach Jianye but are eventually defeated by Ding Gu and Zhuge Jing, who are responsible for Jianye's defense.

Although there is no evidence that Sun Qian is actually involved in the rebellion, Sun Hao has not only Sun Qian but also his mother and his younger brother Sun Jun, by the same mother, executed.

Sun Hao thinks this to be the fulfillment of the prophecy that had prompted his move of the capital to Wuchang, and later this year, he moves the capital back to Jianye.

The senators are practically excluded from the army under Gallienus.

The equites, members of the Roman equestrian order, receive the majority of commands and of provincial governorships; the composition of the army is modified by the creation of new army corps and especially of a strong cavalry, which is placed under the command of a single leader and charged with closing the breaches that the barbarians are opening along the frontiers.

The empire’s period of relative peace ends in 267, when the Goths of the northern Black Sea coast attack Byzantium in alliance with the fleet of the Heruli.

Gallienus leads a large Roman force into Moesia to cut off the army of Goths, three hundred and twenty thousand strong, now retreating by land from its plunder of Aegean coastal cities.

The two armies meet at Naissus (modern Niš, Serbia), where the Romans slaughter the Goths by the thousands.

His attention demanded by the revolt of a usurper, Aureolus, in Italy, Gallienus returns there without further pursuit of the survivors, who flee to armed encampments to the northeast.

Odaenathus has driven the Persians from the Roman provinces of Mesopotamia and Osroëne by 267, and he probably also has brought Armenia back into the empire.

Although he has failed to seize the Sassanian capital of Ctesiphon, he has managed to restore Roman rule in the East, and assembled a small client empire stretching from southern Anatolia to the Red Sea.

He is preparing to drive Gothic invaders from the Roman province of Cappadocia in eastern Asia Minor when he and his eldest son (by his former wife), Herodes (or Herodianus), are assassinated in 267 (or 268).

His queen, Zenobia (in full Septimia Zenobia; Aramaic Znwbya Bat Zabbai) becomes regent for her own young son Wahballat (called Vaballathus in Latin, Athenodorus in Greek).

Zenobia maintains an alliance with the Romans to offset the threat to her kingdom from Persia.

The combined Goth and Herul fleet sails from Byzantium south into the Aegean in 267 to attack various cities of Greece as far south as Sparta, devastating Laconia.

Greece, its weakened frontiers unprotected by Rome, suffers greatly under the ravages of the Goths and pirates.