Some fifteen years before, a severe blow had been struck at the power of the Limerick Vikings under Ivarr, grandson of Ivarr and his sons. The attack made on them at Sulcoit (968) by two princes of the Dal Cais, the brothers Mathgamain and Brian, resulted in victory for the Irish, who took Limerick shortly after.[30] Mathgamain was treacherously murdered in 976, and Brian then became King of Thomond. He soon brought the Kingdoms of Ossory and Leinster under his control, and by the terms of a treaty made in 998 Maelsechnaill consented to leave Brian master of Leth Mogha (_i.e._, the southern half of Ireland). The Leinstermen under King Maelmordha, dissatisfied with this arrangement, began to make trouble and revolted, assisted by the Dublin Norsemen. An important victory was gained over their combined armies at Gleann Mama (Co. Wicklow) in the year 1000 by Brian, who after the battle captured Dublin. King Sihtric (O.N. Sigtryggr), son of Olaf Cuaran, had to submit to Brian’s authority. Having accepted his allegiance Brian married Gormflaith, mother of Sihtric and sister of Maelmordha, and at the same time gave his own daughter to Sihtric in marriage.[31] Brian became _árd-rí_ in 1002, and after that for about twelve years there was peace. Towards the end of that time Gormflaith, who had meanwhile separated from her husband, incited her brother Maelmordha to make war on Brian. Maelmordha and Sihtric began to gather forces for the coming struggle. Sihtric at his mother’s command sought the aid of Sigurthr, Earl of Orkney and of Brodar,[32] a Viking whose fleet then lay off the west coast of Man. Fleets also came from Norway[33] and Iceland to help their kinsmen. The armies under Brian and Maelsechnaill marched towards Dublin, and having encamped near Kilmainham set fire to the district of Fingal (_i.e._, _Fine Gall_, “the Foreigners’ territory”) north of the city. The two armies met at Clontarf on Good Friday morning and the battle, one of the most famous ever fought on Irish soil, raged all that day. The Norsemen suffered a severe defeat, and in attempting to fly for refuge to their ships were slaughtered by Maelsechnaill at Dubhgall’s Bridge, near the Four Courts. Brian himself did not take part in the fight, but he was slain in his tent by Brodar after the battle.[34]