A fyrd was a type of early Anglo-Saxon army that was mobilised from freemen or paid men to defend their Shire's lords estate, or from selected representatives to join a royal expedition.
The system of defence and conscription was reorganised during the reign of Alfred the Great, who set up 33 fortified towns (or burhs) in his kingdom of Wessex.
Ultimately the fyrd consisted of a nucleus of experienced soldiers that would be supplemented by ordinary villagers and farmers from the shires who would accompany their lords.
[1][8] Tenants in Anglo-Saxon England had a threefold obligation based on their landholding; the so-called ‘common burdens' of military service, fortress work, and bridge repair.
as compensation to the king in districts under the English law, and the amount fixed by existing regulations in the Danelaw...[2]England had suffered raids by the Vikings from the late 8th century onwards, initially mainly on monasteries.
[15][16] Each element of the system was meant to remedy defects in the West Saxon military establishment exposed by Viking raids and invasions.
If this entailed transforming the West Saxon fyrd from a sporadic levy of king's men and their retinues into a mounted standing army, so be it.
To maintain the burhs, and the standing army, he set up a system of taxation and conscription that is recorded in a document, now known as the Burghal Hidage; thirty three fortified towns are listed along with their taxable value (known as hides).
Characteristically, all of Alfred's innovations were firmly rooted in traditional West Saxon practice, drawing as they did upon the three ‘common burdens' that all holders of bookland and royal loanland owed the Crown.
[19] Henry I of England, the Anglo-Norman king who promised at his coronation to restore the laws of Edward the Confessor and who married a Scottish princess with West Saxon royal forebears, called up the fyrd to supplement his feudal levies, as an army of all England, as Orderic Vitalis reports, to counter the abortive invasions of his brother Robert Curthose, both in the summer of 1101 and in autumn 1102.