Once they left home, these armies and fleets had to be supplied with food and clothing for the men as well as forage for the horses. Yet if armies of the seventh and eighth centuries were accompanied by servants and a supply train of lesser free men, Alfred found these arrangements insufficient to defeat the Vikings. One of his reforms was to divide his military resources into thirds. One part manned the burhs and found the permanent garrisons which would make it impossible for the Danes to overrun Wessex, although they would also take to the field when extra soldiers were needed. The remaining two would take it in turns to serve. They were allocated a fixed term of service and brought the necessary provisions with them. This arrangement did not always function well. On one occasion a division on service went home in the middle of blockading a Danish army on Thorney Island; its provisions were consumed and its term had expired before the king came to relieve them. This method of division and rotation remained in force up to 1066. In 917, when armies from Wessex and Mercia were in the field from early April until November, one division went home and another took over. Again, in 1052 when Edward's fleet was waiting at Sandwich to intercept Godwine's return, the ships returned to London to take on new earls and crews. The importance of supply, vital to military success, was appreciated even if it was taken for granted and features only incidentally in the sources.