After 877 the _War of the Gaedhil with the Gaill_ notes a period of rest for Ireland, lasting some forty years. This is true to the extent that no large fleets of fresh invaders seem to have come to Ireland during this time--the Vikings were too busy elsewhere, both in England and the Frankish empire--but there were occasional raids from Dublin, Cork, Limerick, Waterford and other towns into various districts of Ireland, and the Norsemen were often at variance amongst themselves. Dissensions in Dublin were particularly violent and so much did they weaken Norse rule there that in 902 Dublin fell into the hands of the Irish. The Vikings were driven abroad, some going to Scotland and others to England, where they besieged Chester (_v. supra_, p. 57). In the year 914 all the old troubles were renewed. Rögnvaldr, a grandson of Ívarr, fresh from a great victory off the Isle of Man, captured Waterford, and two years later Sigtryggr, another grandson of Ívarr regained Dublin. The Irish attempted resistance under the _ardrí_ Niall Glundubh, but he fell with twelve other kings in a fight at Kilmashogue near Dublin in 919. During the next fifty years Ireland was a prey to ceaseless attacks by Norwegians and Danes alike. Towards the close of the 9th century Limerick had become a stronghold of the Norsemen in the west, and from there they made their way up the Shannon into the heart of the country. Cork was settled in the early years of the 10th century, chiefly by Danes, and from there all Munster was open to attack. Waterford and Wexford, which stood as a rule in close connexion with Dublin, served as centres of attack against Leinster. The Irish made a stout resistance under able leaders and Dublin was 'destroyed' more than once. First among these leaders stands Muirchertach 'of the leather cloaks,' son of Niall Glundubh, a hero who came forward about the year 926. His activities were unceasing. He repeatedly attacked Dublin, took a fleet to the Hebrides where he defeated the Vikings, gaining much spoil, and finally in 941 made a circuit of Ireland, from which he brought back as hostages many provincial kings, including the Norse ruler of Dublin. More famous still in Irish song and story was Cellachan of Cashel. He made war against the Vikings in Munster and for a time had the Norse kingdom of Waterford under his control. Similarly he conquered Limerick, and we find him fighting side by side with Norsemen from both these towns. During these fifty years the Norse kingdom in Dublin stood in close relation with the Scandinavian kingdom of Northumbria. Rögnvaldr, who died in 912, ruled there and so did his brothers Sigtryggr (d. 927) and Guðröðr (or Godfrey) (d. 934). The brothers left sons known respectively as Anlaf Sihtricsson and Anlaf Godfreyson. The latter took part in the great fight at Brunanburh and died in 939. Anlaf Sihtricsson was destined to a longer career. He would seem to have