A striking difference between the porphyry portraits of the senior tetrarchs and the marble head of Constantine, the latter statue's clean-shaven face evokes portraits of Trajan, optimus princeps, and the first emperor, Augustus. The distinction between the porphyry and marble portraits points to another salient aspect of the fourth century, the alternation between periods of religious peace and conflict. Constantine's achievement of sole power as Christian emperor changed everything and nothing. His accession is, indeed, treated as a watershed by those who overlook the rapprochement between Christianity and Platonism in the late third century and who view Diocletian's persecution as the culmination of a sustained anti-Christian policy rather than an aberration. After Constantius' death, Julian moved quickly to put his own imprint on Roman power. Receiving reinforcements from Gratian, Theodosius' first task was to deal militarily with the Visigothic problem. In the East, Theodosius too became increasingly hostile toward traditional cult.

Rome was a powerful city-state with a relatively extensive territory, a developed urban centre, an advanced institutional structure and a strong army. Under the kings, armed conflicts with neighbouring communities did take place. There is very little known about the settlements of Latium Vetus during the archaic age.The proliferation of common cults at different sites in Latium does not at first sight seem compatible with the idea of a united Latin League. Intermittent wars between Rome and Veii must have occurred under the monarchy. A number of successful campaigns against the Sabines are recorded. The part played by Camillus in the Gallic saga is demonstrably a late and artificial accretion. In the last years of the fifth century there are clear signs of a more aggressive policy, not only against Veii and its satellites, but also in southern Latium.