At the time of the Viking invasion of Ireland the various provincial kingdoms were held in loose confederation under the authority of the ardrÍ or high king, but these kingdoms stood in constantly shifting relations of friendship and hostility towards one another, and were themselves often split into factions under rival chieftains. There was no national army like the English fyrd. Rather it consisted of a number of tribes, each commanded by its own chief, and though the chief owed allegiance to the king, the bond was a frail one. The tribe was further divided into septs and the army was utterly lacking in any cohesive principle. It is no wonder that for many years the Irish showed themselves quite unable to cope with the attacks of forces so well organised as those of the Norse and Danish Vikings.

In vivid contrast to the chaos in political and military organisation stand the missionary enthusiasm of the Irish church and the high level of education and culture which prevailed among her clergy and literati. In the Orkneys and the Shetlands such names as Papa Westray or Papa Stronsay bear witness to the presence of Irish priests or papae as the Norsemen called them. Irish anchorites had at one time settled in the Faroes (v. supra, p. 6), and when the Norsemen first settled in Iceland (c. 870) they found Irish monks already there. The monastic schools of Ireland were centres of learning and religious instruction for the whole of Western Europe, while Irish missionaries had founded monasteries in Italy, Switzerland, Germany and France.

Unfortunately religion and culture seem to have been almost entirely without influence on the body politic, and as the Vikings had at least in the early days no respect for the religion or the learning of the Irish nation there was nothing to prevent them from devastating Irish monasteries and carrying off the stores of treasured wealth which they contained. No plunder was more easily won, and it was only when they themselves had fallen under Christian influences and had come to appreciate Irish literary and artistic skill that they showed themselves more kindly disposed towards these homes of learning.

One feature must at once strike the observer who compares the Viking settlements in Ireland with those in England, viz. that Viking influence in Ireland is definitely concentrated in the great coast towns—Dublin, Wexford, Waterford, Cork and Limerick—and the districts immediately around them. Irish place-nomenclature bears very definite witness to this fact. Ford in Strangford and Carlingford Loughs, Waterford and Wexford is O.N. fjorÐr, a fjord, -low in Arklow and Wicklow is O.N. lÓ, 'low-lying, flat-grassland, lying by the water's edge.' The O.N. ey, an island, is found in Lambey, Dalkey, Dursey Head, Ireland's Eye (for Ireland's Ey), Howth is O.N. hÖfuÐ, 'a head,' Carnsore and Greenore Point contain O.N. eyrr, 'a sandy point pushing out into the sea.' Smerwick contains the familiar O.N. vÍk a bay or creek, while the Copeland Islands off Belfast lough are the O.N. kaupmannaeyjar, 'the merchants' islands.' All these are found on or off the coast, while the number of Scandinavian names found inland is extremely limited. The most interesting perhaps is Leixlip on the Liffey, a name derived from O.N. laxahlaup, 'salmon-leap.' Donegal, Fingall and Gaultiere are Celtic names, but they mark the presence of the northern Gall or foreigners, while the -ster in Ulster, Leinster and Munster is O.N. -staÐir (pl. of -staÐr, place, abode) suffixed to the old Gaelic names of these provinces.

There was free intermarriage between Norse and Irish (v. supra, p. 56), but the strength of the clan-system kept the races distinct and there was no such infiltration of the whole population as took place in the English Danelagh. This system prevented any such settlement of Norsemen upon their own farms as took place in England, and the invaders lived almost entirely in the coast towns and the districts in their immediate neighbourhood, busying themselves with trade and shipping.

Though the settlements were limited in their extent, we must not underrate their influence on Irish history generally. They gave the impetus there, as elsewhere, to the growth of town life, and from the period of Viking rule dates the origin of the chief Irish towns. To them also was due the great expansion, if not the birth, of Irish trade. Mention has been made of the wealth of Limerick (v. supra, p. 97), drawn chiefly from trade with France and Spain, and the other towns were not behind Limerick. The naval power of Dublin stretched from Waterford to Dundalk, the Irish channel swarmed with Viking fleets, and many of the shipping terms in use in Gaelic are loan-words from the Norse.

It is probably to the trading activities of Vikings from the chiefs ports of Ireland that we owe the sprinkling of names of Norse origin which we find along the Welsh coast from the Dee to the Severn—Great Orm's Head, Anglesey, Ramsey I, Skokholm Island, Flat Holme and Steep Holme, and to them may be due the establishment of Swansea, earlier Sweinesea, Haverfordwest and possibly Bideford, as Norse colonies in the Bristol channel. We know in later times of several Norsemen who were living in Cardiff, Bristol, Swansea and Haverfordwest.

Norse influence in Ireland probably reached its climax in the 10th century. The battle of Clontarf offered a serious check and though there was still a succession of Norse kings and earls in Dublin they had to acknowledge the authority of the ardrÍ. The line of Sigtryggr of the Silken Beard came to an end by the middle of the 11th century, and the rulership of Dublin fell into the hands of various Norse families from other Irish settlements and from Man and the Isles. From 1078-94 it was under the rule of the great conqueror Godred Crovan from Man, and its connexion with that kingdom was only severed finally when Magnus Barefoot came on his great Western expedition in 1103, and brought Man into direct allegiance to the kings of Norway. Celtic influence must have been strong in the Norse families themselves. Several of the kings bear Gaelic names, and it is probably from this period that such familiar names as MacLamont or MacCalmont, MacIver, and MacQuistan date, where the Gaelic patronymic prefix has been added to the Norse names LagmaÐr, Ívarr and Eysteinn. While Norse power in Dublin was on the decline as a political force it is curious to note that the vigorous town-life and the active commerce instituted by the Norse settlers made that city of ever-increasing importance as a centre of Irish life and Irish interests generally, and there can be no question that it was the Norsemen who really made Dublin the capital city of Ireland.

The Norse element remained absolutely distinct, not only in Dublin but also in the other cities in which they had settled, right down to the time of the English invasion in the 12th century. Frequent mention is made of them in the records of the great towns, and they often both claimed and received privileges quite different from those accorded to the native Irish or to the English settlers. They were known to the latter as 'Ostmen' or 'Easterlings,' a term which in this connexion seems to have ousted the earlier Norvagienses or les Norreys, les Norwicheis. The term 'Ostman' doubtless represents O.N. AustmaÐr, a man dwelling to the east. Exactly how or where it first came to be applied to Norsemen it is difficult to say. The word has left its mark in Oxmanstown, earlier Ostmanstown, the district of the city of Dublin assigned to the Ostmen by the English invaders.

Learning and religion in Ireland suffered grievously from Norse attack but not so sorely as in England. There was never a time when so dark a picture could have been drawn of Irish learning as Alfred gives of the state of English learning when he translated the Pastoral Care, and when once the Vikings began to form settlements they were themselves strongly affected by the wealth of literary and artistic skill with which they found themselves brought into contact. The question of Irish influence on Norse mythology and literature is a much vexed one. At present we are suffering from a reaction against exaggerated claims made on its behalf some thirty years ago, but while refusing to accept the view that Norse legends, divine and heroic alike, are based on a wholesale refashioning and recreating of stories from Celtic saga-lore, it would be idle to deny that the contact between the two nations must have been fertile of result and that Norse literature in form, style and subject-matter alike, bears many marks of Gaelic influence.