The political genius of the Conqueror was shown in his appreciation of this danger and in the skill with which he met it.
Large as the estates he granted were, they were scattered over the country in such a way as to render union between the great landowners or the hereditary attachment of great areas of population to any one separate lord equally impossible.

A yet wiser measure struck at the very root of feudalism.

When the larger holdings were divided by their owners into smaller sub-tenancies, the under-tenants were bound by the same conditions of service to their lord as he to the Crown.

"Hear, my lord," swore the vassal as kneeling bareheaded and without arms he placed his hands within those of his superior, "I become liege man of yours for life and limb and earthly regard; and I will keep faith and loyalty to you for life and death, God help me!" Then the kiss of his lord invested him with land as a "fief" to descend to him and his heirs for ever.

In other countries such a vassal owed fealty to his lord against all foes, be they king or no.