...Rome’s eastern boundary is pushed back to…

The Juthungi, an Alemannic tribe in the region north of the rivers Danube and Altmühl in the modern German state of Bavaria, invade Italy in the winter of 259–260, but on their way back they are defeated near Augsburg on April 24–25, 260 by Marcus Simplicinius Genialis (this is recorded on a Roman memorial stone found in 1992).

At this time the Roman Empire loses the Limes area in this region.

The Pannonias, with Valerian’s capture in the East, fall under grave threat from the Germanic tribes, and Regalianus, one of the usurpers proclaimed by the Pannonian legions, dies fighting the invaders.

The defense is concentrated around Sirmium and ...

...Siscia, the ancient fortresses that had been restored by Gallienus; many cities are burned.

Palmyra, ('city of palm trees'), a long-prominent trading city built on an oasis along one of the main routes of east-west trade one hundred and forty miles (two hundred and thirty kilometers) northeast of Damascus, had come under Roman control by the time of the emperor Tiberius.

However, with the Sassanians having supplanted the Parthians in Persia and southern Mesopotamia in 227, the road to the Persian Gulf had soon been closed to Palmyrene trade.

Still relatively autonomous, Palmyra has grown increasingly wealthy and influential due to its tariff on the caravans passing through the city.

In return, the local rulers have policed caravan routes and the border area.

Instability around the Roman-controlled Mediterranean, coupled with the interruption of caravan trade with the East, had led the Romans to set up the personal rule here of the leading Palmyrene family of Septimius Odainath, or Odaenathus, a Roman citizen appointed governor of Syria Phoenice by Valerian.

The year is not known, but already in an inscription dated 258 he is styled "the illustrious consul our lord".

The defeat and captivity of Valerian in 260 has left the eastern provinces largely at the mercy of the Persians; the prospect of Persian supremacy is one that neither Palmyra nor its ruler have any reason to desire.

At first, it seems, Odaenathus had attempted to propitiate the Persian monarch Shapur.

However, when his gifts had been contemptuously rejected (Petr. Patricius, 10) he had decided to throw in his lot with the cause of Rome to prevent his city from falling under Sassanian control.

He thus abandons the neutrality that has made Palmyra's fortune for an active military policy that, while it will add to Odaenathus's fame, in a short time will bring his native city to its ruin.

Before Shapur’s army, returning home in 260 rich in plunder from its sack of Antioch, can cross the Euphrates, Odaenathus deals it a severe defeat, thereby curtailing further Persian aggression in Syria and Asia Minor.

All the stone carvings on Naqsh-e Rustam, in Iran, depict Valerian respectfully as holding hands with Shapur as a sign of his submission.

Shapur uses the remaining captured Roman soldiers in civil engineering and development plans.

Band-e Kaisar (Caesar's dam) is one of the remnants of Roman engineering located near the ancient city of Susa.

The Persians, who have devastated the East just as the Germanic tribes had recently plundered the Rhine and Danube provinces, plunder Cappadocia, ...

...Cilicia, and ...

...Syria.

With the remnants of the army deep in the enemy territory, the soldiers elect to the imperial office Titus Fulvius Iunius Quietus together with his brother Macrianus Minor.

The support of their father, controller of the imperial treasure, and the influence of Balista, Praetorian prefect of the late Emperor Valerian, has proven instrumental their promotion.

Quietus and Macrianus, elected consuls, must now face the lawful Emperor Gallienus, at this time in the West.

Quietus and Balista stay in the eastern provinces, while his brother and father march their army to Europe to seize control of the Roman Empire.

The aged Valerian, now in his late sixties, marches eastward to the Sassanid borders.

According to Shapur's account, he met the main Persian army under command of the King Shapur I, between Carrhae and Edessa and was thoroughly defeated and captured with his entire army.

According to the Roman sources, which are not very clear, the Roman army was defeated and besieged by the Persian forces.

Valerian then tried to negotiate but he was captured and it is possible that his army surrendered after that.

The prisoners included, according to Shapur's claims, many other high-ranking officials, including a praetorian prefect, possibly Successianus.

Valerian is the the only Roman Emperor ever to be taken captive.

According to the Augustan Histories, Valerian's capture had been effected by treachery; the Persians had agreed to meet with him, then seized him when they met.

The beleaguered Roman forces, thrown into disarray by this act, surrender.

Mesopotamia is lost to the empire and ...