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.