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Problem of succession and civil war

From the beginning of the Principate there were no clear rules for the imperial succession, largely because the empire maintained the facade of a republic.

During the early Principate, the process for becoming an emperor relied on a combination of proclamation by the Senate, popular approval, and acceptance by the army, in particular the Praetorian Guard. A family connection to a previous emperor was beneficial, but it did not determine the issue in the way a formal system of hereditary succession would. From the Julio-Claudian dynasty onwards there was sometimes tension between the Senate's preferred choice and the army. As the Senatorial class declined in political influence and more generals were recruited from the provinces, this tension increased.

Whenever the succession appeared uncertain, there was an incentive for any general with support of a sizable army to attempt to seize power, sparking civil war. The most recent example of this prior to the Crisis was the Year of the Five Emperors which resulted in the victory of Septimius Severus. After the overthrow of the Severan dynasty, for the rest of the 3rd century, Rome was ruled by a series of generals, coming into power through frequent civil wars which devastated the empire.