between Ceolwulf and Guthrum. The creation of this system by King Alfred can therefore best be seen as both an in-depth defence of Wessex against possible invasion of Viking forces (such as indeed happened in the period 875-early 878), and as a strategic offensive against the Vikings who controlled Mercia and London at that time. Work on the minting patterns of the coinage of the period has shown that King Alfred was in control of London and the surrounding area until about 877, exactly the time when the Vikings are recorded as partitioning Mercia and taking control of its eastern extent. Thereafter the coins minted in London are only in the name of the Mercian king Ceolwulf. After his decisive defeat of the Vikings at the Battle of Edington in early 878, Alfred was once again able to take the offensive. His victory must have earned him wide acclaim. It is this juncture which seems the most appropriate time for the start of the planning and construction of the system of burhs recorded in the Burghal Hidage. Throughout 878 Guthrum's Vikings were in control of Mercia and, arguably, London, with his base in Cirencester. The creation of burhs at Oxford and Buckingham at this time fits in with the likelihood that Alfred was able to regain control of this area which he had exercised before being deprived of it as a result of the Viking partition of 877, and their siting demonstrates that he was able to initiate a strategic offensive against the Vikings in Eastern Mercia and London. Alfred's standing enabled him to impose a level of conscription on the population of his kingdom to construct the burhs, to act as garrisons behind their defences, and to serve in his new army. Based on the figures provided by the hideage the size of Alfred's conscript army can be deduced. One man per hide would be the equivalent of 27,000 men, whereas one man per 5 hides of land would give 5,500 men. Alfreds practice was to divide his field army into two or three, so with additional support from the royal household troops and those of the leading nobility would provide Alfred with enough manpower to deal with any Viking attacks. The retreat of Guthrum and his band to East Anglia in late 879 and the similar retreat of the Viking army stationed at Fulham, west of London, back