Tetrarchy was replaced by a system of two emperors

Given that Constantine had already crushed his rival Maxentius in 312, the two men decided to divide the Roman world between them. As a result of this settlement, the Tetrarchy was replaced by a system of two emperors, called Augusti: Licinius became Augustus of the East, while his brother-in-law, Constantine, became Augustus of the West. After making the pact, Licinius rushed immediately to the East to deal with another threat, an invasion by the Persian Sassanid Empire.