In September 1011, a large Danish force besieged and sacked the city of Canterbury, gaining entrance to the city, according to the Anglo-Saxon Chronicle, through the treachery of one Ælfmær. A number of high-status captives were taken, including the abbot of St Augustine’s, Leofrun, abbess of Minster-in-Thanet, Bishop Godwine of Rochester, and Ælfweard, the king's high reeve. The most high-profile captive was Archbishop Ælfheah and when the Danes moved on from Canterbury, it was the archbishop they took with them ‘to their ships’. If the Danes hoped to ransom their captive, however, they were to be disappointed. Ælflheah refused to be ransomed and just before Easter 1012, while the Danish force was at Greenwich, their frustration and resentment boiled over and the archbishop was murdered – pelted, so we are told, with ox-heads and bones and then despatched with a blow to the head from an axe. There were undoubtedly many reasons for the Danish warlord Thorkell's attack on the city. Viking armies frequently used Kent and Thanet as a base, Canterbury was undoubtedly a wealthy centre which would yield both treasure and valuable hostages, and the city represented a major ideological and symbolic target. It may also have been a strategic one, sitting as it does on Watling Street. There may, though, have been another reason why Canterbury was an important strategic target; the role its archbishops may have played in the military defence of Æthelred's England. It is this possible role, in particular in relation to naval defence, with which the following discussion is concerned.

The following analysis explores some of the military aspects of the archbishopric, in particular in relation to naval warfare, and locates that exploration in wider discussions about the military organisation of the late Anglo-Saxon state and the role played in it by the church. The starting point is the will of Archbishop Ælfric (d. 16 November 1005), the immediate predecessor of the martyred Ælfheah. A copy of Ælfric's will is preserved among the muniments of Abingdon Abbey, in one of the abbey's twelfth-century cartulary-chronicles, British Library, MS. Cotton Claudius B. vi. Ælfric's will is a rather significant document; it is, as Nicholas Brooks has pointed out, our only surviving pre-Conquest archiepiscopal will. It also contains references to bequests of three ships.