The Brigantes were the major Celtic tribe in what is now Northern England. With a stronghold at the sandstone outcrop on which Manchester Cathedral now stands, opposite Salford's original centre, their territory extended across the fertile lowland by the River Irwell that is now Salford and Stretford. Following the Roman conquest of Britain, General Agricola ordered the construction of a Roman fort named "Mamucium" (Manchester) to protect the routes to "Deva Victrix" (Chester) and "Eboracum" (York) from the Brigantes. Salford was founded when the fort was completed in AD 79, and for over 300 years the "Pax Romana" brought peace to the area. Both the main Roman road to the north, from Mamucium to Ribchester, and a second road to the west, ran through what is now Salford, but few Roman artefacts have been found in the area. The withdrawal of the Romans in AD 410 left the inhabitants at the mercy of the Saxons. The Danes later conquered the area and absorbed what was left of the Brigantes. Angles settled in the region during the Early Middle Ages and gave the locality the name "Sealhford", meaning "ford by the willows". According to the "Anglo-Saxon Chronicle", "Sealhford" was part of the Kingdom of Northumbria until it was conquered in 923 by Edward the Elder.