Dux Britanniarum

Dux Britanniarum was a military post in Roman Britain, probably created by Diocletian or Constantine I during the late third or early fourth century. The Dux (literally, "(military) leader") was a senior officer in the late Roman army of the West in Britain. It is listed in the Notitia Dignitatum as being one of the three commands in Britain, along with the Comes Britanniarum and Count of the Saxon Shore.

His responsibilities covered the area along Hadrian's Wall, including the surrounding areas to the river Humber in the southeast of today's Yorkshire, Cumbria and Northumberland to the mountains of the Southern Pennines. The headquarters were in the city of Eboracum (York). The purpose of this buffer zone was to preserve the economically important and prosperous southeast of the island from attacks by the Picts (tribes of what are now the Scottish lowlands) and against Scots (Irish raiders).

The Dux Britanniarum was commander of the troops of the Northern Region, primarily along Hadrian's Wall. The position carried the rank of viri spectabiles, but was below that of the Comes Britanniarum. His responsibilities would have included protection of the frontier, maintenance of fortifications, and recruitment. Provisioning the troops would have played a significant part in the economy of the area. The Dux would have had considerable influence within his geographical jurisdiction, and exercised significant autonomy due in part to the distance from headquarters of his superiors.

The Notitia Dignitatum lists the garrison along Hadrian's Wall (along with several sites on the coast of Cumbria) under the command of the Dux Britanniarum. Archaeological evidence shows that other units must have been stationed here, which are not, however, mentioned in the Notita. Most of them were established during the 3rd Century.

His troops were limitanei or frontier guards and not the comitatenses or field army commanded by the Comes Britanniarum. Fourteen units in north Britain are listed in the Notitia as being under his command, stationed in either modern Yorkshire, Cumbria or Northumberland. Archaeological evidence indicates there were other posts occupied at the time which are not listed. His forces included three cavalry vexillationes with the rest being infantry. They were newly raised units rather than being third century creations. In addition to these fort garrisons, the dux commanded the troops at Hadrian's Wall: the Notitia lists their stations from east to west, as well as additional forts on the Cumbrian coast. These troops appear to have been third century regiments, although the reliability of the Notitia makes it difficult to infer any solid information from it.

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