He made vigorous but not cruel use of his victory. He demolished his enemies’ strong castles, magazines as they were for pillage no less than bulwarks of feudal independence; but there is nothing to show that he indulged in violence towards persons. He was even generous to the chief concocter of the plot, Guy of Burgundy. He took from him the countships of Vernon and Brionne, but permitted him still to live at his court, a place which the Burgundian found himself too ill at ease to remain in, so he returned to Burgundy, to conspire against his own eldest brother. William was stern without hatred and merciful without kindliness, only thinking which of the two might promote or retard his success, gentleness or severity. There soon came an opportunity for him to return to the king of France the kindness he had received. Geoffrey Martel, duke of Anjou, being ambitious and turbulent beyond the measure of his power, got embroiled with the king his suzerain, and war broke out between them. The duke of Normandy went to the aid of King Henry and made his success certain, which cost the duke the fierce hostility of the count of Anjou and a four years’ war with that inconvenient neighbor; a war full of dangerous incidents, wherein William enhanced his character, already great, for personal valor. In an ambuscade laid for him by Geoffrey Martel he lost some of his best knights, “whereat he was so wroth,” says a chronicle, “that he galloped down with such force upon Geoffrey, and struck him in such wise with his sword that he dinted his helm, cut through his hood, lopped off his car, and with the same blow felled him to earth. But the count was lifted up and remounted, and so fled away.”