For fifty years, the Roman Empire was a revolving door of "Barracks Emperors"—generals who were declared emperors by their troops only to be murdered months later. The empire faced a "perfect storm" of disasters:
The collapse was halted by , a pragmatic reformer who realized the empire was too large for one man to rule. He established the Tetrarchy (Rule of Four), dividing the empire into Eastern and Western halves, each governed by an "Augustus" and a junior "Caesar." The Roman Empire from Severus to Constantine
The Cyprian Plague decimated the workforce and the army. For fifty years, the Roman Empire was a
Constantine legalized Christianity, moving it from a persecuted cult to the favored religion of the state. including the notorious
Severus shifted the empire’s power base away from the Senate and toward the military. While this provided short-term stability, it created a dangerous precedent. His successors, including the notorious , expanded citizenship to nearly all free inhabitants of the empire (the Constitutio Antoniniana ), primarily to increase tax revenue for a ballooning military budget. However, the dynasty ended in chaos with the assassination of Alexander Severus in 235 AD, triggering a half-century of near-total collapse. The Crisis of the Third Century (235–284 AD)