That Dublin owes its importance, if not its origin, to the Norsemen may be inferred from the almost total silence of the historians and annalists regarding it in the years preceding the Scandinavian inroads. It is probable that there was a fort to guard the hurdle-ford where the great road from Tara to Wicklow, Arklow and Wexford crossed the Liffey, but it seems to have played no great part in history before the Norsemen fortified it in 840. Between Church Lane and Suffolk Street they had their _Thing_[89] or meeting-place, which was still to be seen in the seventeenth century; while all along College Green, called Le Hogges[90] and later Hoggen Green by the English, lay their barrows (O.N. _haugar_). During the ninth and tenth centuries the Kingdom of Dublin--known to the Scandinavians as _Dyflinarski_--became one of the most powerful in the west. Its sway extended north to its colonies[91] at the Strangford and Carlingford Loughs, west to Leixlip, south to Wicklow, Wexford[92] and even as far as Waterford. The Dublin kings intermarried with royal families in Ireland, England and Scotland, and between the years 919 and 950 ruled, though in somewhat broken succession, as Kings of York. Limerick (O.N. Hlymrek)[93], the great stronghold on the west coast, had no existence as a city before the ninth century. It was first occupied during the reign of Turgeis by Vikings, who used the harbour as a base for their ships.[94] The only chieftains mentioned in connection with this kingdom during the ninth century are Hona and Tomrir Torra (O.N. Thórarr Thórri), who were slain about the year 860 in attempting to capture Waterford.[95] A few years later Barith (O.N. Barthr) and Haimar (O.N. Heimarr) when marching through Connacht on their way to Limerick, were attacked by the Connachtmen and forced to retreat.[96] The real importance of Limerick, however, dates from the early part of the tenth century when it was colonised by Vikings under Tomar (Thórir) son of Elgi (O.N. Helgi). To secure the fort against attack an earthen mound was built all round, and gates were placed at certain distances leading into the streets and the houses.[97] As a kingdom it was independent, having subject colonies at Cashel, Thurles, Lough Ree and Lough Corrib.[98] It had no connection with Dublin during the tenth century; in fact, there is evidence to show that both royal houses were bitterly hostile towards each another. On one occasion Guthfrith, King of Dublin, led an army to Limerick, but was repulsed with heavy losses by the Vikings there.[99] A few years later (A.D. 929) he expelled Tomar’s successor, King Ivarr of Limerick, and his followers from Magh Roighne (a plain in Ossory), where they had encamped for a whole year. Olaf Godfreyson was equally active. After defeating Olaf Cenncairech and the Limerick Vikings at Lough Ree in 937, he carried them off to Dublin,[100] and that same year probably forced them to fight on his side in the battle of Brunnanburh.