But what is got by force must be maintained by force. These nobles were obliged to build castles all over England, to defend their new property; and, do what he would, the King could neither soothe nor quell the nation as he wished. He gradually introduced the Norman language and the Norman customs; yet, for a long time the great body of the English remained sullen and revengeful. On his going over to Normandy, to visit his subjects there, the oppressions of his half-brother Odo, whom he left in charge of his English kingdom, drove the people mad. The men of Kent even invited over, to take possession of Dover, their old enemy Count Eustace of Boulogne, who had led the fray when the Dover man was slain at his own fireside. The men of Hereford, aided by the Welsh, and commanded by a chief named Edric the Wild, drove the Normans out of their country. Some of those who had been dispossessed of their lands, banded together in the North of England; some, in Scotland; some, in the thick woods and marshes; and whensoever they could fall upon the Normans, or upon the English who had submitted to the Normans, they fought, despoiled, and murdered, like the desperate outlaws that they were. Conspiracies were set on foot for a general massacre of the Normans, like the old massacre of the Danes. In short, the English were in a murderous mood all through the kingdom.