The almost complete absence of any allusion to Irish ships[149] during the eighth and ninth centuries shows that at this time the Irish had no warships to drive back the powerful naval forces of the Vikings. Meeting with no opposition on sea the invaders were able to anchor their fleets in the large harbours, and afterwards to occupy certain important positions along the coasts. In this connection it is interesting to note that the Irish word _longphort_ (a ‘shipstead’; later, ‘a camp’) is used for the first time in the _Annals of Ulster_ with reference to the Norse encampments at Dublin and Linn-Duachaill (840); hence it has been concluded that the early Norse _long-phorts_ were not exactly fortified camps, but ‘ships drawn up and protected on the landside, probably by a stockaded earthwork.’[150] The Annalists tell how, when the Vikings were expelled from Dublin in 902, they fled across the sea to England, leaving large numbers of their ships behind them. It was probably the capture of these vessels that impressed upon the Irish the advantages of this new method of warfare, for they now began to build ships and to prepare to meet the Vikings in their own element.[151] In 913 a “new fleet,” manned by Ulstermen, attacked the Norsemen off the coast of Man but was defeated.[152] Another Ulster fleet commanded by Muirchertach mac Neill, King of Aileach, sailed to the Hebrides in 939 and carried off much spoil and booty.[153] Moreover, the Irish seem to have imitated the Scandinavian practice of “drawing” or carrying their light vessels over land to the lakes and rivers in the interior of the island. Mention is made of Domhnall, son of Muirchertach, who “took the boats from the river Bann on to Lough Neagh, and over the river Blackwater upon Lough Erne, and afterwards upon Lough Uachtair.”[154]