 Although most of Gaul was pacified , regions bordering the English Channel still suffered from Frankish and Saxon piracy . The emperors Probus and Carinus had begun to fortify the Saxon Shore , but much remained to be done . For example , there is no archaeological evidence of naval bases at Dover and Boulogne during 270 – 285 . In response to the pirate problem , Maximian appointed Mausaeus Carausius , a Menapian from Germania Inferior ( southern and western Netherlands ) to command the Channel and to clear it of raiders . Carausius fared well , and by the end of 285 he was capturing pirate ships in great numbers . 
