The evidence that the duces reported to the magistri dates from well before the Notitia from the 360 s with several examples in Ammianus Marcellinus e g in 361 the magister equitum Orientis Ursicinus sent orders to the dux of Mesopotamia Cassianus to evacuate the civilian population of several towns in his military district and to move his troops to Amida Ammianus XVIII 7 3 The late Roman army s operations were based on a close cooperation between the frontier forces and the diocesan comitatus