The art of diplomacy had never altogether slumbered since much earlier times.  The king who owed his crown to William’s father, and who could have no ground of offence against William himself, easily found good pretexts for meddling in Norman affairs.  It was not unnatural in the King of the French to wish to win back a sea-board which had been given up more than a hundred years before to an alien power, even though that power had, for much more than half of that time, acted more than a friendly part towards France.  It was not unnatural that the French people should cherish a strong national dislike to the Normans and a strong wish that Rouen should again be a French city.  But such motives were not openly avowed then any more than now.  The alleged ground was quite different.  The counts of Chartres were troublesome neighbours to the duchy, and the castle of Tillieres had been built as a defence against them.  An advance of the King’s dominions had made Tillieres a neighbour of France, and, as a neighbour, it was said to be a standing menace.  The King of the French, acting in concert with the disaffected party in Normandy, was a dangerous enemy, and the young Duke and his counsellors determined to give up Tillieres.  Now comes the first distinct exercise of William’s personal will.  We are without exact dates, but the time can be hardly later than 1040, when William was from twelve to thirteen years old.  At his special request, the defender of Tillieres, Gilbert Crispin, who at first held out against French and Normans alike, gave up the castle to Henry.  The castle was burned; the King promised not to repair it for four years.  Yet he is said to have entered Normandy, to have laid waste William’s native district of Hiesmois, to have supplied a French garrison to a Norman rebel named Thurstan, who held the castle of Falaise against the Duke, and to have ended by restoring Tillieres as a menace against Normandy.  And now the boy whose destiny had made him so early a leader of men had to bear his first arms against the fortress which looked down on his birth-place.  Thurstan surrendered and went into banishment.  William could set down his own Falaise as the first of a long list of towns and castles which he knew how to win without shedding of blood.

When we next see William’s distinct personal action, he is still young, but no longer a child or even a boy.  At nineteen or thereabouts he is a wise and valiant man, and his valour and wisdom are tried to the uttermost.  A few years of comparative quiet were chiefly occupied, as a quiet time in those days commonly was, with ecclesiastical affairs.  One of these specially illustrates the state of things with which William had to deal.  In 1042, when the Duke was about fourteen, Normandy adopted the Truce of God in its later shape.  It no longer attempted to establish universal peace; it satisfied itself with forbidding, under the strongest ecclesiastical censures, all private war and violence of any kind