ABSTRACT
In the summer of 387, the fragile peace that had held for four years between the usurper and Valentinian II suddenly broke when Magnus Maximus’ battle-hardened forces launched a sudden attack on Italy via the Cottian Alps. Magnus Maximus’ failure to capture Valentinian II during his invasion was to cost him politically. When Valentinian fled directly to Thessalonica to seek the protection of the eastern emperor, Theodosius was gifted his casus belli. Magnus Maximus’ failure to capture Valentinian II during his invasion was to cost him politically. When Valentinian fled directly to Thessalonica to seek the protection of the eastern emperor, Theodosius was gifted his casus belli. Previously, Magnus Maximus as Augustus in the west had represented a future threat. Now, Magnus Maximus as a next-door-neighbour with a declared heir was a clear and present danger to the survival of Theodosius’ own dynasty.
