Not all of Diocletian's plans were successful: the Edict on Maximum Prices (301), his attempt to curb inflation via price controls, was counterproductive and quickly ignored.
Although effective while he ruled, Diocletian's tetrarchic system collapsed after his abdication under the competing dynastic claims of Maxentius and Constantine, sons of Maximian and Constantius respectively.
The army unanimously saluted Diocles as their new augustus, and he accepted the purple imperial vestments.
He raised his sword to the light of the sun and swore an oath disclaiming responsibility for Numerian's death.
From at least 297 on, imperial taxation was standardized, made more equitable, and levied at generally higher rates.
Weakened by illness, Diocletian left the imperial office on 1 May 305, and became the first Roman emperor to abdicate the position voluntarily.
He lived out his retirement in his palace on the Dalmatian coast, tending to his vegetable gardens.
Galerius, aided by Diocletian, campaigned successfully against Sassanid Persia, the empire's traditional enemy. Diocletian led the subsequent negotiations and achieved a lasting and favourable peace.
Diocletian separated and enlarged the empire's civil and military services and reorganized the empire's provincial divisions, establishing the largest and most bureaucratic government in the history of the empire.