Coinage of Valerian and Gallienus

[5][6] When Valerian was raised to the purple (Oct. 22, 253), the Roman Senate ratified the appointment of the troops of Rhaetia as emperor, at the same time elevating his son Gallienus to the rank of Caesar.

[24] In the case of Valerian and Gallienus, in addition to dynastic advantages, the association of the adult son with his father's throne[18] allowed for two emperors perfectly capable of governing, thus giving double force to imperial rule.

[25] And so father and son divided the administration of the empire and departed as soon as possible for their respective destinations - Gallienus, after being appointed ordinary consul in 254, to the West along the Limes Germanicus,[26] and Valerian to the East.

Numerous farms and crops had been destroyed, if not by barbarians, then by bands of brigands and by Roman armies seeking sustenance during military campaigns fought against both external and internal enemies (usurpers to the imperial purple).

Added to all this was a constant forced recruitment of soldiers, to the detriment of the manpower employed in the agricultural countryside, resulting in the abandonment of many farms and vast areas of fields to be cultivated.

[5][6] Towards the end of 253 a new incursion of Goths devastated the region of Thessalonica: the Germanic people failed to conquer the city, which, however, only with difficulty and much effort was liberated by the Roman armies of the new emperor Valerian (see coin below from the mint of Viminacium).

[29][30] At the same time the Franks and Alemanni were stopped in their attempt to break through the Roman limes by the young Caesar Gallienus, who earned for these successes the appellation "Restitutor Galliarum" and "Germanicus maximus.

[32] In 257 the Rhine front of Germania Inferior was disrupted by new Frankish attacks, who managed to push as far as Mogontiacum, where they were stopped by the advancing Legio VI Gallicana, of which the future emperor Aurelian was military tribune.

Today, modern critics seem to re-evaluate his actions, in an attempt to save at least the “central heart” of the Roman Empire, thus creating the basis for a territorial reunification, which occurred, shortly thereafter, with the Illyrian emperors (268-282).

In late 267 and early 268, during the siege of Milan by Gallienus against Aureolus (who had his headquarters in Mediolanum), the mint produced coins of the usurper, Postumus, at the head of the Gallic Empire.

[51] It was probably Gallienus who decided on the final abandonment of all the territories east of the Rhine and north of the Danube, due to the continuous invasions of the neighboring Germanic tribes of the Alemanni, and the simultaneous secession of the western part of the empire, led by the governor of Upper and Lower Germania, Postumus.

[55][56] At the same time, along the Limes of Lower Germania, hordes of Franks managed to seize the legionary fortress of Castra Vetera and besieged Cologne, while sparing Augusta Treverorum (today's Trier).

"[54] For these successes, he assumed the appellation of "Restitutor Galliarum" ("restorer of Gaul"), also deciding to recruit bands of newly defeated Frankish soldiers into the ranks of his army to fight against their own "brothers," as testified by Aurelius Victor.

[61][62][63] The barbarian hordes also brought devastation to the hinterland of the province of Macedonia,[64] until Gallienus, near the mouth of the river Nestos, intercepted one of the Gothic armies and slaughtered them (spring of 268).

Realizing the impossibility of simultaneously protecting all the provinces of the empire with a static line of men positioned close to the frontier, Gallienus developed a practice that had begun in the late second century under Septimius Severus (with the placement of a legion, the Legio II Parthica, a few kilometers from Rome), that is, by positioning a strategic reserve of well-trained soldiers ready to intervene where they were needed in the shortest possible time (cavalry contingents at Mediolanum, Sirmium,[68] Poetovio[69] and Lychnidos).

This measure the senate, the city, and men of every age received with approval.As a result of these victorious campaigns, imperial authority in the East was restored; Emperor Gallienus was able to celebrate a triumph, thanks to his "rector Orientis," Odaenathus, who shared his victories with his eldest son Hairan and earned the honorific title of king of kings, as opposed to that of the Sasanian king, Shapur I. Valerian's death had the main effect of causing Gallienus' enemies to take advantage of it, both by threatening the imperial borders and its provinces (since Gallienus alone could not defend all the Roman territories) as well as by supporting numerous local usurpations that guaranteed the imperial presence there (such as Piso,[84] Valens,[85][86] or Mussius Aemilianus,[85][87] in addition to the more famous Ingenuus,[88] Regalianus[88] and Aureolus).

[85][89] And so beginning in 260 (until about 274), the Roman Empire suffered the secession of two vast territorial areas, which, however, also allowed its survival:[90] Eutropius wrote: So when Gallienus abandoned the state, the Roman Empire was preserved by Postumus in the West and Odaenathus in the East.In addition to the secessions highlighted above, Gallienus had to cope with a continuous series of usurpations, mostly among the commanders of the eastern (Macrianus Major, Macrianus Minor, Quietus and Balista) and Danubian military provinces (a period referred to as the “thirty tyrants”).