Probus has spent his six-year reign thus far in continual frontier warfare against hostile tribes on the Rhine and Danube, complicated by insurrections in Britain, Gaul, and the East.

His policy of allowing outside tribes to settle within the empire will prove dangerous.

Fourth-century writers attest to his intense interest in agriculture: when not campaigning against barbarians or rebels, Probus has put the soldiers to work, making them drain land, erect buildings and defenses, build bridges, and even plant vineyards in Gaul, Spain, and Britain.

Consequently, army moral is at a low point in the spring of 282, when Probus sets out for Sirmium to prepare a campaign against the Persians.

The armies stationed in Raetia and Noricum along the Upper Danube in September 282 proclaim as emperor the praetorian prefect, whose name before the accession may have been Marcus Numerius Carus.

Born, probably, at Narbo (modern Narbonne) in Gaul, but educated at Rome, he had been a senator, and had filled various civil and military posts before his appointment as prefect of the Praetorian Guard by Probus earlier in the year.

Probus immediately sends troops to engage Carus, but they defect to the usurper.

As this news reaches Probus' camp, his troops, who resent his strict discipline and their being detailed to agricultural reclamation work in the Balkans, decide to change their allegiance to Carus.

In late September, mutineers evidently kill the emperor in Sirmium, not far from his place of birth, where he is buried.

Carus, on learning of Probus's death, severely punishes the murderers but is himself suspected of having been an accessory to the deed.

He sends a messenger to inform the Senate, without seeking its approval, that he has succeeded to the imperial position.

As Probus had enjoyed respect among the senators, Carus sees to his predecessor's deification.

Without visiting Rome, he next arranges for the elevation of his adult sons Carinus and Numerian to the rank of Caesar (junior emperor).

The cult of Mithra, which recognizes the two powers of good and evil, has becomes popular among Roman legionaries and receives official patronage under Carus.

News soon reaches him that the Sarmatians and the Quadi have crossed the Danube and invaded Pannonia.

Together with Numerian, Carus enters Pannonia and there decisively defeats the barbarians, inflicting enemy casualties of as many as sixteen thousand and taking twenty thousand prisoners.

Carinus is sent by his father to the army of the Rhine.

Sassanid Persia, in decline since the death of Shapur, is currently riven by civil war between Bahram II and his brother, the kushanshah Hormizd, who is trying to establish an independent eastern empire.

Bahram II is said to have ruled at first tyrannically, and to have greatly disgusted all his principal nobles, who had gone so so far as to form a conspiracy against him, and intended to put him to death.

The chief of the Magi, however, had interposed, and, having effectually alarmed the king, brought him to acknowledge his wrong and to promise an entire change of conduct.

The nobles upon this had returned to their allegiance; and Bahram, during the remainder of his reign, is said to have been distinguished for wisdom and moderation, and to have rendered himself popular with every class of his subjects.

Emperor Wu, having become more concerned about whether his brother Prince You would seize the throne if he died, had in 282 sent Prince You to his principality, even though there was no evidence that Prince You had such ambitions.

Having grown ill, Prince You dies in anger in 283.

The old contest for northern Mesopotamia, with its fortified cities of Carrhae, Nisibis, and Edessa, continues.

The Sassanians are even more eager to regain and retain control of Armenia because there the Arsacid dynasty still survives and turns for protection to Rome, with which, in consequence, new wars continually break out.

Carus, having announced in the winter of 282-83 that he seeks to achieve the reconquest of Mesopotamia planned by Probus, sets out for Persia, again accompanied by Numerian, leaving Carinus in charge of the western portion of the empire.

Bahram II is still preoccupied with defending his position against his brother Hormizd, viceroy of the eastern provinces.

Probus’s successor Carus, proceeding through Thrace and Asia Minor, invades Mesopotamia unopposed in 283, annexing the province and capturing first Seleucia, then …