Before he set out from Normandy, William had had a difficult time in getting his own Norman barons to follow him in his quest to gain the English crown. Most considered it suicide, if only because of the difficulty in making the crossing over the English Channel in the relatively primitive boats that they used. Thus, William had a problem in terms of gaining military assistance in his campaign. The solution to that problem was presented by one of his advisers, Lanfranc, the man a Lombard abbot and monastic teacher who after the Conquest became Archbishop had previously helped gain papal approval of CanterburyWilliam's uncanonical marriage to his wife, Matilda.

Lanfranc's solution (for which he was eventually awarded the position of Archbishop of Canterbury after the Conquest) came in the form of casting the invasion as a crusade to bring the English church into submission to the [[papacy]]. David Howarth, in his ''1066 The Year of the Conquest'', explains: