After the Battle of Edington in 878, Alfred established a network of fortified settlements, called burhs, in Wessex to protect his people and territory against Viking attacks, and when Æthelred accepted Alfred's lordship the burhs were extended into Mercia. One of the burhs was Worcester, where Æthelred worked with its bishop and used the standing Roman walls in the town's defences. Over the next two generations Worcester was transformed from an ecclesiastical settlement to a town with a diverse population of craftsmen.