Constantine legalized Christianity, moving it from a persecuted cult to the favored religion of the state.
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) The Roman Empire from Severus to Constantine
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 empire faced a "perfect storm" of disasters: