The military events of the campaign which followed are obscure, and can be traced with little chronological certainty. We hear of some sort of hostile encounter at Maromme near Rouen shortly after Easter, but we know nothing about it, save that a certain knight in the service of Robert d’Estouteville was slain.[107] The chief military undertaking of the campaign was undoubtedly the siege of Bayeux. Against Bayeux and its commander, Gontier d’Aunay, the king had a particular grievance because of the capture and imprisonment of his supporter Robert Fitz Hamon.[108] Accordingly, he assembled all his forces, including his allies from Maine and Anjou, and laid siege to Bayeux.[109] Gontier d’Aunay went out to meet him and promptly handed over his prisoner, Robert Fitz Hamon. He declined, however, to make any further concessions, and Henry refused to raise the siege.[110] But the garrison failed to justify the confidence which their commander had placed in them,[111] and, in an assault, Henry managed to fire the city.[112] A high wind carried the flames from roof to roof, and soon the whole place was swept by the conflagration. Bishop Odo’s beautiful cathedral and several other churches, the house of the canons attached to the cathedral, the house of a distinguished citizen named Conan, almost all the buildings in the town, in fact, except a few poor huts, were destroyed. Many of the inhabitants, who in their terror had fled to the cathedral, perished in the flames. The place was given over to be plundered by the Manceaux and the Angevins, and Gontier d’Aunay and many of the garrison were taken captive.[113]

Caen was the next important place to fall into Henry’s hands; but here no siege was necessary. The fate of Bayeux had spread consternation throughout the duchy, and served as a terrible warning of what might be expected, if resistance proved unsuccessful; and the burgesses of Caen had little love for the duke, who had made them feel the weight of his exactions. Accordingly, a conspiracy was formed among certain of the leading citizens, Enguerran de Lacy and the ducal garrison were expelled, and the town was basely surrendered to the English, to the intense indignation of the common people, among whom the duke appears to have been popular.[114] Robert Curthose was himself in Caen at the time, and, learning of the plot at the last moment, he fled headlong to the Hiémois. His attendants, who followed closely after him, were held up at the gate, and his baggage was rifled.[115] In grateful appreciation of this easy conquest, the king conferred the manor of Dallington, in England, upon the wealthy burgesses who had betrayed the second town of Normandy into his hands.[116]

Having gained possession of Bayeux and Caen, the king marched upon the strong castle of Falaise. But at this moment he temporarily lost the powerful support of the count of Maine. “At the request of the Normans,” it is not said of what Normans, Helias of La Flèche withdrew from the contest; and Henry found his forces so weakened that he was obliged to abandon the attack upon Falaise until the following year. Some desultory fighting occurred, however, in which one of the king’s knights, Roger of Gloucester, was mortally wounded by a shaft from a crossbow.[117] Almost simultaneously, apparently, with the operations about Falaise, Robert and Henry attempted to make peace. In the week of Pentecost (21-28 May), they met in conference at the village of Cintheaux near Falaise and endeavored for two days to arrive at an agreement. But the king was prepared to offer no terms which the duke could accept, and the negotiations were broken off.[118]

There was, indeed, no good reason why Henry should have made peace, except to gain time while he reëquipped himself for the completion of the enterprise upon which he had embarked. The sources speak specifically only of the conquest of Bayeux and of Caen during the campaign of 1105. Yet it is certain that the extension of the king’s domination through the influence of English gold and through the voluntary surrender of numerous minor strongholds had gone much further than this.[119] Eadmer, writing of the situation as he himself saw it in Normandy in July 1105, was able to say that almost all Normandy had been subjected to the king. The power of the duke had been reduced to such a point that hardly any one obeyed him or rendered him the respect due to a prince. Almost all the barons spurned his authority and betrayed the fealty which they owed him, while they ran after the king’s gold and silver and surrendered towns and castles on every side.[120] Yet with all his success, Henry was unable to complete the conquest of Normandy in a single campaign. Even hogsheads may be drained, and the method of waging war with gold and silver, as well as with the sword, had been costly. Before completing his task, he found it necessary to return to England and replenish his supplies.[121]

But before returning to England, Henry had a diplomatic problem of great importance to solve. Since 1103 Anselm had been living in exile, and the investiture controversy had been in abeyance. But the archbishop had at last grown restive and had decided to resort to the extreme measure of excommunicating the king. Rumor of the impending sentence spread throughout France, England, and Normandy, and caused not a little uneasiness.[122] In the midst of his struggle for Normandy with Robert Curthose, Henry could not but view this new danger with grave concern; and he never showed to better advantage than in the broad and statesmanlike way in which he met the crisis. Through the mediation of Ivo of Chartres and of the king’s sister, Countess Adela of Blois, a conference was arranged between him and the archbishop, to be held on 22 July at Laigle on the Norman frontier. There he received Anselm with the utmost courtesy, and, since he was in no position to drive matters to a rupture, he showed himself sincerely desirous of arriving at an amicable adjustment. Anselm, too, was disposed to compromise; and they were soon able to agree upon the broad lines of a final settlement of the long controversy. Messengers were despatched to Rome by both the king and the archbishop to secure the ratification of the Holy See.[123] The details of a formal concordat had yet to be arranged; but friendly relations were now completely restored between Henry and Anselm, and the ecclesiastical crisis was averted. In August[124] the king returned to England, “and what he had won in Normandy continued afterwards in peace and obedient to him, except those who dwelt anywhere near Count William of Mortain.”[125]

In point of fact, William of Mortain and Robert of Bellême appear to have been almost the only really powerful barons in Normandy who still supported the duke, and the loyalty even of the Bellême interests could probably have been shaken had the king so desired. Before Christmas Robert of Bellême paid a visit to England and sought an interview with the king. It would be hazardous to infer that he, too, was contemplating a desertion of the ducal cause; but whatever his mission, he failed to accomplish it, and, departing from the king’s Christmas court ‘unreconciled,’ he returned to Normandy.[126]

It was not long before the king had a more important visitor from beyond the sea. Early in 1106 Robert Curthose himself crossed the Channel, and, in an interview with the king at Northampton, besought him to restore the conquests which he had won from him in Normandy.[127] The duke must have felt his situation almost desperate, yet it is difficult to imagine what inducements he expected to offer, or how, in the light of his past experience, he could have dreamed of gaining a concession or any consideration from his unscrupulous brother. Henry could well afford to be obdurate, and he returned a flat refusal to the duke’s demands. Robert withdrew in anger, and returned to his duchy;[128] and Henry wrote immediately to Anselm, who was still in Normandy, announcing his own crossing for 3 May following. It is not quite easy to see why he should have stated in his letter that Robert had parted with him amicably,[129] but the ways of diplomacy are often obscure.

Robert Curthose now knew beyond all question what he had to expect, and, as formerly in the crisis of his struggle with William Rufus, he sought aid from without. If the unsupported statement of William of Malmesbury may be accepted, he appealed to his overlord, the king of France, and to Robert of Flanders in a conference at Rouen;[130] but the far-seeing diplomacy of Henry I had anticipated him,[131] and he was able to obtain no assistance.

Meanwhile, Henry had completed his preparations for a second invasion of Normandy, and “before August”[132] he crossed the Channel. He landed without opposition, but soon afterwards, apparently, an attempt was made to take him in an ambush. Abbot Robert of Saint-Pierre-sur-Dives, the notorious simoniac, entered into a secret compact with the duke and some of his barons at Falaise to betray the king into their hands. Then, while Reginald of Warenne and the younger Robert d’Estouteville, with a considerable body of knights, installed themselves in the fortress which the abbot had constructed within the precincts of his monastery, he paid a visit to the king at Caen and treacherously agreed to surrender the fortress to him, at the same time advising him to come quietly with but a few knights to take it, in order to avoid giving the alarm. But Henry did not ride blindly into the trap that was set for him. Placing himself at the head of a force of seven hundred horse, he came suddenly upon the monastery at daybreak after an all night’s ride; and, as soon as he had apprised himself of the true situation, he launched an instant attack, burned both the monastery and the fortress, and took Reginald of Warenne, Robert d’Estouteville, and many of their men captive. Reënforcements on their way from Falaise saw the conflagration and turned back in flight. The attempted ambush had been turned into a notable royal victory. The treacherous Abbot Robert was also taken. Thrown across a horse ‘like a sack,’ he was brought before the king, who expelled him from the land with the declaration that, if it were not for his sacred orders, he would have him torn limb from limb.[133]