Final answer:
Diocletian reformed the Roman Empire by increasing the army's size, dividing military command, implementing the Tetrarchy for shared rule, and introducing economic policies to curb inflation. His legacy includes the introduction of smaller administrative provinces and the structure for church governance. Despite his reforms, subsequent civil wars led to Constantine's ascent to power and the unification of the empire.
Step-by-step explanation:
Emperor Diocletian is notable for his substantial reforms of the Roman Empire, including the separation of the military chain of command from the bureaucratic hierarchy. To secure the borders against Persia and the Germanic tribes, he restructured the Roman army by increasing its size, investing in infrastructure such as military roads, and incorporating heavy cavalry influenced by Persian military tactics. Diocletian created smaller legions, subsequently reducing each commander's potential power to prevent coups. His reorganization was designed to stabilize the Roman Empire and diminish the likelihood of military usurpation of power.
In 284 CE, Diocletian was declared emperor and implemented lasting reforms that contributed to the empire's eventual eastward shift. He implemented the Tetrarchy, a shared rule system comprising four emperors, two senior (augustus) and two juniors (caesar), each governing specific regions with their own capitals. Diocletian's economic reforms included the Edict on Maximum Prices to control inflation and stabilize the currency.
Moreover, Diocletian subdivided the Empire into smaller provinces for more efficient governance, established larger units called dioceses overseen by vicars, and laid a foundation for church administration that continues to the present day. The Tetrarchy's aim was to create orderly succession and end the cycle of power struggles within the empire. However, following Diocletian's abdication in 305 CE, civil wars ensued, leading to Constantine's rise to power, who later unified the empire under his sole rule.