Everything was now ready for the great advance against the Danes. Derby fell in 917, while in the next year Leicester yielded without a struggle. Their fall was accompanied by the submission of the men of Derbyshire and Leicestershire. At the same time the inhabitants of York declared themselves ready to enter the service of Mercia. Edward fortified Bedford in 915, Maldon and Towcester in South Northamptonshire in 916. Again the Danes from Northampton and Leicester tried to break through the steadily narrowing ring of forts and they managed to get as far south as Aylesbury, while others from Huntingdon and East Anglia built a fort at Tempsford in Bedfordshire near the junction of the Ivel and the Ouse. They besieged a fort at 'Wigingamere' (unidentified) but were forced to withdraw. Edward gathered an army from the nearest garrison towns, besieged, captured, and destroyed Tempsford (915). In the autumn he captured Colchester and a Danish attempt on Maldon failed. Edward now strengthened Towcester and received the submission of Earl Thurfrith (O.N. Ðorröðr) and all the Danes in Northamptonshire as far north as the Welland. Huntingdon was occupied about the same time and the ring of forts around East Anglia brought about the submission of the whole of that district, Cambridgeshire making a separate compact on its own account. In 918 Edward built a fort just south of Stamford and soon received the submission of the Danes of South Lincolnshire, and in the same year occupied Nottingham, building a fort and garrisoning it with a mixed English and Danish force. He was now ruler of the whole of Mercia owing to the death of his sister Aethelflæd, and in 919 he fortified Thelwall in Cheshire, on the Mersey, and rebuilt the old Roman fort at Manchester. In 920 he built a second fort at Nottingham and one at Bakewell in Derbyshire. The reconquest of the Danelagh was complete and Edward now received the submission of the Scots, the Strathclyde Welsh, of Regnold (O.N. Rögnvaldr) of Northumbria, and of English, Danes and Norsemen alike. The Danish settlers accepted the sovereignty of the West Saxon king and henceforward formed part of an expanded Wessex which had consolidated its power over all England south of a line drawn roughly from the Humber to the Dee.