The Romans invaded Britain in AD 43 on the orders of the emperor Claudius, and throughout the remaining ten years of his reign, Roman rule was gradually imposed on the peoples of southern England. By the time Nero came to the throne in AD 54, the province of Britannia extended up to the Severn estuary in the west and the Humber in the east, having absorbed the territories of half a dozen tribes. All this time, the tribes of modern-day Wales remained defiant, but the Brigantes, who occupied a huge area in northern England, had entered into treaty relations with Rome, and no real contact had been made with the tribes further north. The reign of Nero ended in civil war across the empire. In AD 70, a new emperor, Vespasian, inaugurated an expansionist policy in Britannia, with campaigning in the territory of Wales and northern England. By AD 77, Roman armies stood on the threshold of present-day Scotland. This title covers the seven years of campaigning in Wales, northern England and Scotland that followed, culminating in the decisive battle of Mons Graupius in AD 83 that saw the devastation of the Caledonian confederation under the legendary Calgacus at the hands of the Roman forces of the provincial governor, Gnaeus Julius Agricola. The battle saw the loss of 10,000 Caledonians, while only 360 Romans were killed. The victory at Mons Graupius saw the whole of the island of Britannia lying pacified, and this was to prove the high-water mark of the Roman Empire in the north. Following unrest elsewhere in the empire, the north of Scotland was abandoned and Roman power in Britain now entered a phase of retreat and retrenchment. Never again would Roman arms stand on the edge of the world.