 Building of Hadrian's Wall along the line of Agricola's earlier garrisons began in 122 AD and was mostly completed in less than ten years, such was the efficiency of the Roman military.It ran from Bowness on the Solway Firth across the north of the county and through Northumberland to Wallsend on the Tyne estuary, with additional military installations running down the Cumbrian coast from Bowness to Risehow, south of Maryport, in an integrated fashion (and with forts at Burrow Walls and Moresby that were perhaps not part of the system).There were several forts and milecastles along the Cumbrian half of the wall, the largest of which was Petriana (Stanwix), housing a cavalry regiment and which was probably the Wall's headquarters (perhaps indicating that the serious unrest was taking place in this western sector of the frontier, or perhaps it was halfway along the distance of the Wall plus the Solway coast installations).