Diocletian emerged the last man standing after 50 years of Roman turmoil. The Crisis of the Third Century sapped the Roman Empire's dynamism. Civil wars, barbarian incursions, and economic dislocation nearly ruined the empire. Diocletian stepped into the vacuum and restored Rome. He attempted political, military, religious, and economic reforms, but most failed. In the end, the reform-minded emperor's true legacy was the restoration of order within the Roman Empire.
The Crisis of the Third Century began in 235 with the end of the Severan Dynasty. Over the next fifty years, almost 80 people claimed the imperial throne. Officially, 26 men assumed imperial purple between Alexander Severus and Diocletian. These men varied in abilities, but all failed to restore order to the empire. Crisis after crisis beset the empire. Civil wars created factions and opened the border for barbarian incursions, plague and famine depleted the population, the economy collapsed, and the empire actually splintered into three entities at one point.
Diocletian emerged from the military to restore order. He built on the work of his predecessors and managed to bring the disparate forces to heel. The new emperor managed to get the empire working again. Most importantly, he ended the series of civil wars and eliminated potential challengers to his power. The Roman Empire began to function once more.
The new emperor wanted to ensure Rome's continued existence and unity. As a result, he initiated political reforms designed to end succession crises. He split the empire into four administrative districts ruled by four different emperors. Diocletian created a hierarchy amongst the four emperors so when one died or retired, another could slide into the role without conflict. In a sense, he created a system similar to the American executive branch. If a president dies, the vice president assumes the office. In Rome, if an Augustus died or retired, the Caesar elevated to the higher office.
The tetrarchy, or rule by four, did not survive Diocletian's retirement. However, his military reforms did help restore order and ensure Roman power for two centuries in the west and another millennium in the east. He increased the size of the military, created more legions, made them more mobile, and built up Roman defenses. This arrangement served emperors well until barbarians overwhelmed the empire by their sheer numbers in the fifth century.
Diocletian believed Roman weakness derived from religion. He felt the Romans needed to return to their ancestor's religion in order to fully restore the empire. As a result, Diocletian initiated a purge of Christians. The emperor blamed the bizarre cult for the empire's ills. No one knows for sure how many died in the Great Persecution. However, it failed in the end. Christianity became the empire's official religion shortly after Diocletian's death. Ironically, the church infrastructure saved western civilization after Rome fell.
Religion had little effect on the Roman economy. On the other hand, political turmoil caused by civil wars and barbarian invasions completely disrupted the western economy. On top of this, overspending and currency devaluation further hampered economic recovery. Diocletian attempted to reform the currency with no luck. He also initiated price and wage controls to stop inflation. This also failed spectacularly. The emperor had no concept of supply and demand, wage controls created a disincentive to work, and price controls led to high inflation. On top of this, people ignored the edict even under penalty of death. Despite Diocletian's best efforts, the western economy did not recover until the Carolingian Renaissance.
Diocletian retired after two decades in office. He attempted many reforms with varied success. His political reforms did not survive his retirement. The economic and religious reforms completely failed. On the other hand, the military and bureaucratic reforms helped steady the empire. In the end, Diocletian's legacy was Rome's continued existence. His efforts helped the empire survive for another two centuries.