In the years of 1100 and 1101 Magnus was occupied with the Swedish war. In 1102, however, he went forth on his last expedition, which this time was undertaken directly against Ireland. There is a letter preserved from Muircertach to the celebrated Anselrn, Archbishop of Canterbury (Anselmi epistolae, iv. 85), in which the Irish king thanks the prelate for the assistance given to his son-in-law Arnulf. The letter must have been written about this time.
What the Chronicle tells about his sending his shoes to King Muircertach and the unconditional submission of the latter, seems to be a mere fable; yet if something like it took place, it must have been in the winter immediately preceding the expedition. From the Irish and Welsh annals, as well as from Orderic, we learn how matters stood with Muircertach. His war with Donald O'Lochlan raged more fiercely than ever; and although, on the whole, Muircertach had the upper hand, yet Donald was an obstinate and dangerous foe, against whom he felt the necessity of strengthening himself through alliance with other powerful rulers. Shortly before, King Henry I. (Beauclerc) had ascended the English throne, excluding, as is well known, his senior brother Robert, Duke of Normandy, with whom he had to sustain a hard feud. Among the Barons who embraced the party of Robert were the two brothers of the above mentioned Earl Hugh Montgomery, who was killed by King Magnus, Robert of Belesme, who after the fall of Hugh had purchased his earldom, having besides many other possessions in England, as well as in Normandy, and Arnulf, who had Dyved and Pembroke in Wales.
Robert made an alliance with the three Welsh princes, Jorwerth, Cadogan, and Meredith, sons of Blethyn, and Arnulf sought the alliance of Muircertach, asking, through ambassadors, his daughter Lafracot in marriage, to which Muircertach immediately gave his consent, promising not only to support Arnulf against the English king, but also to make him his successor. In this manner a rather strong league bad been formed against King Henry; and as the allied lords and princes, especially the two Montgomerys, as avengers of their brother, must at the same time have been the enemies of King Magnus, this prince was consequently brought somehow into a friendly relation with the English. monarch, notwithstanding that Henry, if the conjecture which we ventured to utter above be right, had married the destined bride of Magnus. Yet it must be remembered that Magnus himself, during his absence, had married the Swedish princess Margaret, and no doubt given up all enmity, if any such existed, against Henry; while through the peace concluded in 1098 with Eadgar of Scotland, the friend and protégé of the English king, a reconciliation between their party and King Magnus may already be said to have been partly effected.
From the Welsh chronicles and the Irish annals that Magnus before visiting Ireland landed at Man, where he, as it were, established his headquarters, erecting forts as before, and making a personal visit to Anglesey, where prince Griffith received him cordially, and, as mentioned above, gave him permission to cut what timber he might require for his fortifications
Meanwhile matters had gone wrong with the Hiberno-British league. Robert of Montgomery was declared an outlaw, and several of his castles taken; one of the Welsh princes had been induced to embrace the king's part; Arnulf of Montgomery had betaken himself to the court of Muircertach, craving assistance, but the latter, far from being able to afford any, on the contrary was expecting aid from Arnulf against Magnus. 16 Under these circumstances Muircertach found it safest first to make peace, or truce for a yeare with Donald O'Lochlan, and then to enter into negotiations with Magnus. In what manner these negotiations were conducted is nowhere told; we learn only from the Irish annals that the peace was concluded for a yeare (no doubt to be renewed at the expiration of this term), and that Muircertach gave his daughter in marriage to Sigurd, the son of Magnus, who was now proclaimed king of the western possessions.
It has already been mentioned that the Saga wrongly speaks of this marriage as having taken place during the former expedition of Magnus, and that it likewise wrongly makes Magnus and Muircertach together conquer Dublin in 1102, this conquest having been effected during the first expedition of Magnus in 1093. Yet it would seem, and it must be taken almost for certain, that by the treaty of 1102 Muircertach ceded to Magnus the district of Dublin, which may have been regarded as an appendage of the kingdom of Alan; partly because it is not likely that Magnus should have accorded to Muircertach the peace, and moreover, as will be seen, his powerful assistance against Donald O'Lochlan for nothing, partly because Ordericus states expressly, that Magnus established colonies of Northmen even in Ireland,18 which could not have been done if he had not got a territory to dispose o£ And lastly, if there be any truth at bottom in the anecdote about the shoes, it is to be supposed that Muircertach acknowledged Magnus as his suzerain, and paid a kind of homage to him as such, not, however; intending to keep any of the given promises longer than necessity compelled him to do so. Ordericus states expressly that Muircertach acted treacherously towards Magnus, as well as towards Arnulf.
It is easy to see from the following facts that the principal object of Muircertach was to crush his Irish rivals, and that to this end he deemed it necessary to secure the powerful assistance of Magnus, with the hope, perhaps, of having afterwards an opportunity to get rid of him. The treaty was strengthened by giving hostages from both sides. Among the Norwegian hostages was the Icelandic poet Gisl Illugason, from whose poem in honour of King Magnus several fragments are quoted in the Saga, to corroborate the facts there mentioned.
The Saga of the holy bishop John of Hólar in Iceland, Biskupa Sogur. Here the following curious story is told :-With the hostages there was a Norwegian, who boasted of being well versed in the Irish language, and offered to salute King Muircertach in the name of the others, which being allowed, he said, "male díarik," which, however, means " damned be thou, O king! " Then another of the Norwegians put in his word, saying : " My Lord, this man is only the slave of the Norwegians; " to which the king replied "algeira ragall," which means "difficult to know is the dark riddle" (gáta), or "road" (gata). Those of our readers who are acquainted with the Irish language may perhaps be able to suggest the correct forms of the Irish words here reproduced, no doubt in a very bad shape.
Arriving in Ireland, Magnus was friendly received by Muircertach, and no doubt got possession of Dublin with its district, where he effected the settlements spoken of by Orderic, which appear rather to have been castles and strongholds, like those erected in Man and the Isles. In the winter, the Saga tells, Magnus was the guest of Muircertach in his residence of Kinkora, and in the next spring, it is farther told, both kings went to Ulster, where they fought many battles, and conquered a part of Ulster. This is true, in so far, as really the hostilities between Muircertach and the northern Irish commenced anew in 1103, no doubt because the truce had expired, and that several battles were fought as we learn from the Irish annals. But as to the conquests in Ulster, it is far from any such thing having taken place; as, on the contrary, Muircertach and his allies were the losing party.
The Irish annals say, that Muircertach, having encamped with his army, consisting of the men from Munster, Leinster, Ossory, Meath, and Connaught, on the plains of Cobha (in the north part of Downshire), he divided his forces, going with one part to Dalaraide (the district on the coast southeast of Lough Neagh), leaving the rest at Cobha, where during his absence it was attacked and completely routed by Donald O'Lochlan on the 5th of August. Among the number of the killed there were also, according to the Irish annals, " foreigners from Dublin," three of whom are expressly named, viz. " Thorstain mac Eric," " Poll mac Amaind," and " Beollan armuinn," the two former, at least, being entirely Scandinavian (Thorstain Ericson and Paul Amundson); maybe these " foreigners" were Norwegians from the army of Magnus, although it is to be supposed that the Norwegian king with his main force was on board his fleet, ravaging the coasts, while Muircertach made war on land, and that the diversion of the latter to Dalaraide was effected in order to meet and operate in conjunction with Magnus.
Other northern septs: The Uí Echach na hÁrda, of the ards of county Down. The sept of O hEirc, chiefs of Hy-Fiachra Finn, were noted by O'Hart in the barony of Massarene, modern co. Antrim. Within Scotland, Ninian's pupil Caranoc and successor reamains in Stirlingshire is thought to have engaged in missions to Pictland and to Dalriada as the Pictish district of Ulter when St. Blane labored in Strathclyde. According to Bede, writing in Northumbria at the beginning of the 8th century, hardly gives any information apart from what he has taken from Gildas.
In any case it is evident that the defeat at Cobha put an end to the operations, as it is expressly stated in the Saga that the expedition to Ulster having been ended, Muircertach returned to Kinkora, and Magnus prepared to go home; these preparations, however, must have taken place immediately after the battle at Cobha, as the fall of Magnus occurred only nineteen days afterwards, on St. Bartholomew's Day.
This catastrophe is said by Ordericus to have been caused by the treachery of the Irish, who induced him to leave the ships, and hazard himself with a small force into the interior of the country, making him believe that they intended to offer their submission, but afterwards suddenly attacking him with immensely superior numbers. This seems very probable in itself, but it ought to be remembered, that the Saga, founded upon traditions from the men who were present at the battle themselves, does not give the least hint of anything like treachery on the part of Muircertach.
Magnus, it is said, wanting meat for the support of his army, despatched men to Muircertach, requesting him to furnish the necessary number of cattle; which request having been complied with, but the march of the cattle taking longer time than expected, Magnus, growing impatient, went imprudently too far up in the country to see if they did not appear, and was attacked by the Irish. If, at this time, Muircertach had' already returned to Kinkora, it seems not likely that Magnus should have sent his men so far; probably, however, Muircertach had not yet left the neighbourhood of Dalaraide, and in this case could not comply otherwise with the request than by compelling the inhabitants, or helping the Norwegian emissaries in compelling them, to yield up the prescribed number of cattle, a measure by which the men of Ulster would no doubt feel greatly exasperated, and become eager for revenge, without any instigation from Muircertach, or concerting of treacherous measures with him.
On his second campaign, Magnus went to Man, and with a huge fleet attacked Dublin and attempted to bring the submission of Muircertach mac Toirrdelbach, the Uí Briain King of Munster. The campaign resulted in an alliance between the two kings, and the arranged marriage of Magnus' son Sigušr to Muircertach's daughter Bláthmin. The alliance mitigated the threat of Domnall mac Lochlainn, King of Ailech, bringing stability to the Irish Sea world, and security to Magnus' new Irish Sea "Empire." However, it all went wrong when Magnus was killed on his way back to Norway on a minor raid in Ulster. Much of Magnus' work lay in ruins.
Indeed, the annals of Ulster, where the particulars must have been well known, say only that Magnus was attacked and killed by the Men of Ulster on a plundering expedition. The particulars of the battle are most circumstantially and forcibly told in the Saga, which, however, does not mention, what is told only in the Chronicle of Man, that the body of the king was buried at St. Patrick's Church in Down. Maybe his remains may still be found there. It is evident that he was buried by the Irish, not by his own men, who were obliged to leave the body on the battlefield, and that this must have been in the neighbourhood of Down; his fleet probably still lying at the same spot where it was when the battle was fought at Cobha.
At the death of Magnus, his men abandoned all newly acquired possessions in the West, and hastened homewards, taking with them prince Sigurd, who left his bride, the daughter of Muircertach, saying, according to the Saga, that all lords in the West, Scotch as well as Irish, were odious to him. This certainly might be construed as indicating that Sigurd himself suspected the Irish of treachery against his father, yet such an interpretation of the words is by no means necessary. After all, however, Muircertach turned out to be really a traitor; immediately after the fall of Magnus he courted very submissively the friendship of the English king, took his daughter back from Arnulf, and gave her to another man; nay, he even planned schemes against his life, which also, perhaps, Arnulf might have lost, if he had not been warned in time, and made his escape to Normandy.