What did diocletian do to address some of the problems caused by an expanding empire?

divided the empire into two halves

moved the capital to byzantium

hired mercenary soldiers to protect rome

established the third triumvirate

Divided the empire into two halves

Explanation:

At the time when Diocletian came to power, the Roman Empire was in severe decline. He began many reforms to undo the turmoil of the last century but he is most memorable for splitting Rome into two pieces. The Eastern Roman Empire that was under him, and the Western Roman Empire that was under the rule of his colleague Maximian. He essentially saved Rome from total collapse.