In the course of the imperial reforms under Emperor Diocletian new military offices were introduced in Britain and Gaul. At that time the limes (border wall/marker) of the Saxon coast were established on both sides of the English Channel. The castles guarding the heavily exposed sections and estuaries were partially restored or modified from existing structures. Their garrisons had the task of repelling raiders and impeding the access of invaders to the interior. The main responsibility for securing both coasts was in the middle of the 4th century placed in a Comes Maritimi Tractus. In 367, an invasion of Britain by several barbarian peoples, almost completely wiping out units of the local provincial forces, killing the coastal commander Nectaridus. His area of responsibility must have been divided thereafter—by 395 at the latest—into three military districts. This most likely was also to prevent a military commander from having too many soldiers under his command, thus enabling him to start an uprising (such as the usurpation of the British fleet commander Carausius). For the Gallic part of the Saxon coast, two new ducal regions were created, which existed until the early 5th century.barbarica conspiratio, Ammianus 27,8,1–6, Peter Salway 2001, S. 281
