From the earliest times until the Confiscation of Ulster, the southern frontier of that province made invasion difficult. It was protected by broad lakes and rivers and deep woods, and probably also by the remains of that great ancient line of earthworks of which I have spoken in an earlier lecture. When Ulster was invaded by land, the approach was almost always on the eastern side from Dundalk or Ardee towards Armagh, or on the western side between Lower Loch Erne and the sea-coast. Maurice FitzGerald planned to invade it, building castles as he gained ground, both on east and west. In 1244 we read of a new castle built at Donaghmoyne, near Carrickmacross. Next year, 1245, FitzGerald was summoned by Henry III. to aid him in an invasion of Wales. He went across with an Irish army and his subject king of Connacht. The enterprise did not answer expectation, and Henry sent FitzGerald back deprived of the viceroyship. FitzGerald nevertheless resumed his plan of conquest, the new viceroy, FitzGeoffroi, seconding him. In 1247 he built a castle at Sligo, as a basis of operations towards the Erne. This done, the next step was to seize and fortify the passage of the Erne at Ballyshannon; but he found the king of Tir Conaill there on guard. FitzGerald ordered his Connacht auxiliaries to pretend a retirement and to make a circuit crossing the Erne some miles further up. The stratagem succeeded. The king of Tir Conaill, attacked in front and flank, was defeated and fell in the fight. At his side fell a chief named MacSomhairlidh, "the son of Sumarlidi." This name is the first sign of the Hebridean Galloglach element in Irish wars. Next year, 1248, the justiciar FitzGeoffroi cooperated in the campaign against Ulster. He led an army to Coleraine, where already there was a castle on the eastern side of the Bann. He built a bridge and built a second castle on the western side, thus securing a new way for invasion. Brian O'Neill did not remain inactive. He brought ships over land from Loch Foyle to Loch Erne, and attacked and demolished a castle at Belleek, newly built by FitzGerald. Fast upon this followed a revolt of Feidhlimidh O'Connor. The viceroy marched to FitzGerald's aid and Feidhlimidh was driven out, but returned next year and continued to hold his own.