bours; if they collected a force of knights or constructed castles, so must he. The impetus to this development came not from the invasions by Vikings and Magyars which were contained and then defeated in the course of the tenth century, nor from economic decline and the dictates of a natural economy; on the contrary the process reached its height during the eleventh century at a time of economic recovery and happened earliest and most intensively in those regions which were most advanced economically, Flanders in particular. The thrust came from the anxiety of lords to maintain, consolidate, and extend their lordships.

As primogeniture became the norm, in northern France during the tenth century, then in Germany and southern France during the eleventh, there was a dual pressure on lords to find fresh lands both for members of their own families and for those of their vassals. Emigration might reduce this pressure. Nobles from many northern French lands found their way to England in the wake of the Norman Conquest or joined in the Norman settlement of southern Italy and Sicily. Others, mainly during the twelfth century, took service with the king of Scotland. Many went to fight the heathen in the Holy Land or Spain, as much to redeem their souls as to secure fresh lands (indeed, one early twelfth-century chronicler took it as proven that the First Crusade had been shaped by God because for him it went against all nature for there to be 'such a contempt for material things in the hearts of savage and greedy men'). Even so formidable pressures remained. They could be met in several ways: by the acquisition of fresh territories which could then be distributed, by the regulation of vassals' tenures as closely as possible, permitting inheritance at will rather than as a matter of course, or by granting greater rights to vassals and by moderating or waiving demands for service from them. But such rights were not unlimited and the bonds so created were not likely to be any more enduring than those established by cruder acts of patronage. Kings and lords made use of all three of these techniques of control and conciliation, often simultaneously, but each left immense probability of friction and dispute, and at worst of civil war.

Underlying stability is a less obvious feature of the period,

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