Abstract
The summer of 357 was a problematic time of overlapping troubles for the Roman Empire in the West. Ammianus Marcellinus is our best or unique source about these events. His account, as usual, shows many signs of strong bias in favour of Julian. But past scholarship has missed other points that enable us to tell a very different tale on this year of warfare. The strategic planning of Constantius II and the tactical leadership of Barbatio were not at all so bad as Ammianus brilliantly enjoins us to believe.