By this organization, which was universal throughout the kingdom, sixty thousand cavalry could, with little delay, be called into the field. Those who held by this military service had their allotments divided into so many knights' fees, and each knight's fee was to furnish one mounted and armed soldier. The great vassals retained a portion of their land as their demesnes, having tenants who paid rents and performed services not military. But, under any circumstances, the vassal of the crown was bound to perform his whole free service with men and horses and arms. It is perfectly clear that this wonderful organization rendered the whole system of government one great confederacy, in which the small proprietors, tenants, and villeins had not a chance of independence; and that their condition could only be ameliorated by those gradual changes which result from a long intercourse between the strong and the weak, in which power relaxes its severity and becomes protection. In the ordinance in which the King commanded "free service" he also says, "we will that all the freemen of the kingdom possess their lands in peace, free from all tallage and unjust exaction." This, unhappily for the freemen, was little more than a theory under the Norman kings. There were various modes of making legal exaction the source of the grossest injustice. When the heir of an estate entered into possession he had to pay a "relief," or _heriot_, to the lord. This soon became a source of oppression in the crown; and enormous sums were exacted from the great vassals. The lord was not more sparing of his men. He had another mode of extortion. He demanded "aid" on many occasions, such as the marriage of his eldest daughter, or when he made his eldest son a knight. The estate of inheritance, which looks so generous and equitable an arrangement, was a perpetual grievance; for the possessor could neither transmit his property by will nor transfer it by sale. The heir, however remote in blood, was the only legitimate successor.