Abstract
Imperial succession was always problematic in the Roman empire and was born with the empire itself. Therefore, succession was a potential threat to the political stability of the empire. This paper discusses a number of situations of imperial succession as described in the Res Gestae by Ammianus Marcellinus, the most important historian of the fourth century. After discussing shortly the rise to power of Julian (361–363), Valentinian (364–375), and Valens (364–378) as instances of potential political (and military) insecurity, the main part discusses the power vacuum as a consequence of the sudden and unexpected death of the emperor Julian in the heartland of Persia. This was a particular moment of crisis. Thanks to the capable crisis management of the military and civic officials within a few hours a successor was nominated by the consistorium and subsequently acclaimed by the army. Although initially not considered for Julian's succession, the dynamics of the crisis made Jovian the unanticipated ruler over the Roman empire. He managed to deal with a critical and almost hopeless situation. He quickly concluded a settlement with Shapur without surrendering that not only brought the army safely back to Roman territory but also established relatively peaceful relations between Rome and Persia for many years to come. In that sense the crisis of 363 became a turning point.
