William may have felt that Robert's willingness to accept the crown of England from the rebel barons gave him the right to take what he could get in Normandy, though probably he was not particularly troubled by the question of any moral justification of his conduct. Opportunity would be for him the main consideration, and the growing anarchy in the duchy furnished this. Private war was carried on without restraint in more than one place, and though the reign of a weak suzerain was to the advantage of the rapacious feudal baron, many of the class preferred a stronger rule. The arguments also in favour of a union of the kingdom and the duchy, which had led to the rebellion against William, would now, since that attempt had failed, be equally strong against Robert. For William no motive need be sought but that of ambition, nor have we much right to say that in such an age the ambition was improper. The temptation which the Norman duchy presented to a Norman king of England was natural and irresistible, and we need only note that with William II begins that determination of the English kings to rule also in continental dominions which influences so profoundly their own history, and hardly less profoundly the history of their island kingdom, for centuries to come. To William the Conqueror no such question could ever present itself, but the moment that the kingdom and the duchy were separated in different hands it must have arisen in the mind of the king. But if William did not himself care for any moral justification of his plans, he must make sure of the support of his English vassals in such an undertaking; and the policy of war against Robert was resolved upon in a meeting of the court, probably the Easter meeting of 1090. But open war did not begin at once. William contented himself for some months with sending over troops to occupy castles in the north-eastern portion of Normandy, which were opened to him by barons who were favourable to his cause or whose support was purchased. The alarm of Robert was soon excited by these defections, and he appealed to his suzerain, King Philip I of France, for aid. If the policy of ruling in Normandy was natural for the English king, that of keeping kingdom and duchy in different hands was an equally natural policy for the French king. It is hardly so early as this, however, that we can date the beginning of this which comes in the end to be a ruling motive of the Capetian house. Philip responded to his vassal's call with a considerable army, but the money of the king of England quickly brought him to a different mind, and he retired from the field, where he had accomplished nothing.