It will be shown that neither of these causes can be held to explain the failure. The conquest was brought to a standstill and the tide was turned more than half a century before the Bruce invasion. The principal factor was national sentiment, intensified and supplied with a more definite political form under a sense of national oppression. Hardly had the sentiment of nationalism acquired this form when a new and unexpected force came to its aid. The value of this new force was crystallised into a proverb by one of the Feudal lords, Sir Robert Savage of the Ards in East Ulster: "Better is a castle of bones than a castle of stones." The policy of conquest by incastellation crumbled away before the castles of bones built up first under the Irish princes of Ulster, afterwards in Connacht, and in time all over Ireland. By a castle of bones, Sir Robert Savage meant a well organised, well armed, and well trained permanent field force. From the days of the Fiana down to the thirteenth century, there had been no such force under the command of an Irish king. Irish law and custom were unfavourable to soldiering as a profession. The new force was not supplied by Irishmen. It came from the Norse kingdom of Argyle and the Hebrides. Already before 1263, when the rulers of this kingdom ceased to be subject to Norway, we find Hebridean leaders helping the Irish of Ulster. Before the close of the thirteenth century, we find organised bodies of Hebridean fighting men on the Irish side, and a common name for them already in use, Gallógláich, a word which was afterwards transplanted into English in the form "galloglasses." It means "foreign soldiers." You may learn from a number of books that the galloglasses were heavy-armed Irish soldiers. They were men of Argyle and the Hebrides who came over to Ireland for military service, or descendants of such men who were settled in Ireland and held on to the profession of soldiers. It may possibly be too much to say that no Irish were admitted to their ranks; but with one very doubtful instance every officer of galloglasses that I find named from the thirteenth century, when they are first heard of, until the seventeenth century, when they are last heard of, bears a Hebridean surname; and the surnames of the majority of their commanders indicate descent from Sumarlidi, who established the kingdom of the Hebrides and Argyle in the twelfth century. A century or so after the introduction of the galloglasses, we find native Irish troops established in imitation of them. These, however, bear a distinct name, _buannadha_, "buonies," meaning men on permanent service. It was this reintroduction of permanent military organisation that ultimately broke down the force of feudal conquest. But as this preceded the Bruce invasion, so also it will be seen that it was itself preceded by a very definite national rally of the free Irish. Let us trace the course of events in greater detail.