By the time of Constantine’s death in 337 AD, the Roman Empire was unrecognizable from the one Severus had inherited. The Mediterranean world had shifted from a pagan, Rome-centered principate to a Christian, East-leaning autocracy. This "Late Antiquity" set the stage for the Byzantine Empire in the East and the eventual rise of medieval Europe in the West.
After Diocletian’s retirement, the Tetrarchy dissolved into civil war. Out of the smoke emerged . Following his victory at the Battle of the Milvian Bridge in 312 AD—where he claimed to have seen a vision of a cross in the sky—Constantine fundamentally altered the course of Western civilization. The Roman Empire from Severus to Constantine
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." By the time of Constantine’s death in 337
The silver content of Roman coins dropped to nearly zero. The collapse was halted by , a pragmatic
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)
He took an active role in church doctrine, seeking to unify the faith.
Diocletian stabilized the economy through price edicts and reorganized the military into mobile field armies. However, he is also remembered for the "Great Persecution," a final, violent attempt to suppress the rising tide of Christianity and restore traditional Roman values.