This concept map on Diocletian and Constantine summarizes the major changes in the Roman Empire during the 3rd and 4th centuries AD. It explains Diocletian's reforms, the Tetrarchy, the reorganization of the army and tax system, and the persecution of Christians. The map also covers Constantine's reforms, the Edict of Milan (AD 313), freedom of worship, the foundation of Constantinople, and the new political organization of the Empire. A clear and effective study resource for reviewing Ancient Roman history in primary and lower secondary school.