Whatever the original destination of the expedition which the duke and the king had prepared, they suddenly turned it against their obstreperous brother who was presuming to resist them, and soon drove him to the last extremity.[103] Henry’s resistance was a forlorn hope from the beginning. Hugh of Avranches and other nobles who had previously been his enthusiastic supporters against the duke, but who had important holdings across the Channel, now prudently reflected that it would be unwise to incur the wrath of William Rufus, and in view of the meagreness of Henry’s resources they discreetly surrendered their strongholds.[104] Thus deserted and overwhelmed on every side, Henry was driven from the mainland; but by favor of some of the monks[105] he gained entrance to the monastery of Mont-Saint-Michel, and there in the famous abbey fortress he determined to make a last stand.
For two weeks, about the middle of Lent,[106] William Rufus and Robert Curthose besieged him.[107] Stretching their forces about the bay of Mont-Saint-Michel from Genêts on the north past Ardevon to the Couesnon on the south, they completely invested the Mount upon the landward side, and, as Henry was without naval resources, this constituted an effective blockade. The duke had his headquarters at Genêts, while the king established himself at Avranches.[108] The scene was enlivened from day to day by the knightly joustings of the opposing forces upon the sandy beach.[109] William Rufus himself was once engaged in these feats of arms to his grave humiliation, being unhorsed by a simple knight.[110] Meanwhile, the besieged garrison was rapidly being reduced to desperate straits. Though the food supply was adequate, there was great lack of water. Manifestly a close maintenance of the blockade would quickly have forced a surrender. But Robert Curthose had too chivalrous a heart to let his brother suffer from thirst. He directed the guards to keep their watch a little carelessly in order that Henry’s servants might occasionally pass through the lines and fetch water.[111] Wace affirms that he even sent Henry a tun of wine.[112] Such chivalrous and impractical generosity was beyond the comprehension of William Rufus, who upbraided the duke and came near disrupting their alliance and withdrawing from the siege.[113] But Henry soon saw the hopelessness of his plight, and, “reflecting upon the changing fortunes of mortals, determined to save himself for better times.” He offered to capitulate upon honorable terms, and William and Robert readily agreed to his proposals, and allowed him to march out with his garrison under arms.[114] Henry’s subsequent fortunes are obscure. Ordericus Vitalis recounts some heroic details of his wanderings and vicissitudes in exile.[115] But it is clear that some definite reconciliation was arranged with his brothers before the end of summer, for early in August we find him crossing with them to England to join in an expedition against the king of Scotland.[116]