Great Roman Civil War (Gaul Rising)

The Great Roman Civil War was the longest and most destructive civil war in the history of the Roman Empire. This war was the climax of a long period of political instability in the Roman Empire. The causes of the war were the near-simultaneous but separate challenges to the rule of Emperor Aurelian by Probus and Pinianus, the emergence of Julius Asclepiodotus as a third contender for the Roman throne after his successful mutiny against Aurelian, and a clash between forces loyal to Probus and forces loyal to Asclepiodotus that quickly got out of control.

The Long Crisis of the Roman Empire
A turning point in Roman history occurred in 235 AD. That year, Alexander Severus was murdered by his own troops. His troops then proclaimed a general named Maximinus Thrax the new Emperor. Thrax was not liked by the Senate; so when Gordian, the governor of Africa Proconsularis, rebelled, the Senate was eager to back him. The rebellion failed, and Thrax prepared to march on Rome to punish the Senate. Ultimately, Thrax's invasion of Rome failed, so he met the same fate as his predecessor: murder by dissatisfied troops under his command.

Maximinus Thrax's reign set the tone for the next several decades. There had never been any formal procedure for imperial succession; and the rise of Thrax was seen by many generals and provincial governors as indicating that rebelling against the current Emperor was a perfectly acceptable means of becoming Emperor, and the message that was widely taken from downfall of Thrax was that any failure by the current Emperor or any claimant to the throne could be used as a pretext for rebellion. The following cycle dominated the next four decades: a general would gain broad recognition as Emperor, immediately have to contend a rebellion or external invasion, and in many cases be killed by his own troops, who would then align themselves with a new contender for the throne.

There were two problems that developed as a result of the political instability. One was that as Roman generals turned on each other, they had less manpower and resources to devote to defending the borders against increasingly dangerous Germanic tribes. Germanic invaders frequently raided cities throughout the empire. Another consequence of the political instability was a debasement of the Roman currency, resulting in hyperinflation: whenever a general would declare himself Emperor, he would promptly order the minting of a large supply of coins to pay his troops with.

By 260, the local authorities were beginning to take up the primary responsibility for defending their jurisdictions against external invaders. In the Syrian provinces, a general named Lucius Septimius Odaenathus was nominally loyal to Emperor Gallienus, but was in fact highly autonomous. (He died in 267, after which his wife, Zenobia, took over his realm and openly rebelled against the central government.) In western Europe, Postumus declared himself Emperor; but rather than seeking control over the whole empire, he simply focused on administering the provinces that were loyal to him.