Bristol, and was with difficulty persuaded not to punish the bishop by depriving him of his office. Stephen found a difficult task before him at Bristol. Its capture by assault was impracticable. A siege would have to be a blockade, and this it would be very hard to make effective because of the difficulty of cutting off the water communication. Stephen's failure to command the hearty and honest support of his own barons is also evident here as in almost every other important undertaking of his life. All sorts of conflicting advice were given him, some of it intentionally misleading we are told.[38] Finally he was persuaded that it would be better policy to give up the attempt on Bristol for the present, and to capture as many as possible of the smaller castles held by the rebels. In this he was fairly successful. He took Castle Gary and Harptree, and, after somewhat more prolonged resistance, Shrewsbury, which was held by William Fitz Alan, whose wife was Earl Robert's niece. In this last case Stephen departed from his usual practice and hanged the garrison and its commander. The effect of this severity was seen at once. Many surrenders and submissions took place, including, probably at this time, the important landing places of Dover and Wareham. In the meantime, at almost exactly the date of the surrender of Shrewsbury, affairs in the north had turned even more decidedly in the king's favour. About the end of July, King David of Scotland, very likely as a part of the general plan of attack on Stephen, had crossed the borders into England, for the third time this year, with a large army gathered from all his dominions and even from beyond. Treason to Stephen, which had before been suspected, now in one case at least openly declared itself. Eustace Fitz John, brother of Payne Fitz John, and like him one of Henry I's new men who had been given important trusts in the north, but who had earlier in the year been deprived by Stephen of the custody of Bamborough Castle on suspicion, joined King David with his forces, and arranged to give up his other castles to him. David with his motley host came on through Northumberland and Durham, laying waste the land and attacking the strongholds in his usual manner. On their side the barons of the north gathered in York at the news of this invasion, the greatest danger of the summer, but found themselves almost in despair at the prospect. Stephen, occupied with the insurrection in the south, could give them no aid, and their own forces seemed unequal to the task. Again the aged Archbishop Thurstan came forward as the real leader in the crisis. He pictured the sacred duty of defence, and under his influence barons and common men alike were roused to a holy enthusiasm, and the war became a crusade. He promised the levies of the parishes under the parish priests, and was with difficulty dissuaded, though he was ill, from encouraging in person the warriors on the battlefield itself. A sacred