realised that they were outmanoeuvred, struck off north-westwards and wintered at Cwatbridge near Bridgnorth. The next year, 896 (or 897), they gave up the struggle. Some retired to Northumbria, some to East Anglia. Those who had no connections in England returned to the continent. Military reorganisation The Germanic tribes who invaded Britain in the fifth and sixth centuries relied upon the unarmoured infantry supplied by their tribal levy, or fyrd, and it was upon this system that the military power of the several kingdoms of early Anglo-Saxon England depended. The fyrd was a local militia in the Anglo-Saxon shire in which all freemen had to serve; those who refused military service were subject to fines or loss of their land. According to the law code of King Ine of Wessex, issued in , Wessex's history of failures preceding Alfred's success in 878 emphasised to him that the traditional system of battle he had inherited played to the Danes' advantage. While the Anglo-Saxons and the Danes attacked settlements for plunder, they employed different tactics. In their raids the Anglo-Saxons traditionally preferred to attack head-on by assembling their forces in a shield wall, advancing against their target and overcoming the oncoming wall marshalled against them in defence. The Danes preferred to choose easy targets, mapping cautious forays to avoid risking their plunder with high-stake attacks for more. Alfred determined their tactic was to launch small attacks from a secure base to which they could retreat should their raiders meet strong resistance. The bases were prepared in advance, often by capturing an estate and augmenting its defences with ditches, ramparts and palisades. Once inside the fortification, Alfred realised, the Danes enjoyed the advantage, better situated to outlast their opponents or crush them with a counter-attack because the provisions and stamina of the besieging forces waned. The means by which the Anglo-Saxons marshalled forces to defend against marauders also left them vulnerable to the Vikings. It was the responsibility of the shire fyrd to deal with local raids. The king could call up the national militia to defend the kingdom but in the case of the Viking raids, problems with communication and raising supplies meant that the national militia could not be mustered quickly enough. It was only after the raids had begun that a call went out to landowners to gather their men for battle. Large regions could be devastated before the fyrd