 Complete the following phrase:  Some small measure of stability again returned at this point, with the empire split into a Tetrarchy of two greater and two lesser emperors, a system that staved off civil wars for a short time until 312 AD. In that year, relations between the tetrarchy collapsed for good and Constantine I, Licinius, Maxentius and Maximinus jostled for control of the empire. In the Battle of Turin Constantine defeated Maxentius, and in the Battle of Tzirallum, Licinius defeated Maximinus. From 314 AD onwards, Constantine defeated Licinius in the 