Failing in an attempt to arrange terms, and also in obtaining the help which he solicited from France, O'Neill was utterly routed by the O'Donnells at Letterkenny; and seeking safety in flight, he threw himself on the mercy of his enemies, the MacDonnells.
Carried on a litter at the head of his clan he gave battle to O'Neill, whom he defeated with severe loss in prisoners and cattle; but he died of his wound immediately afterwards near Letterkenny, and was succeeded in the chieftainship by his brother Donnell Oge, who returned from Scotland in time to withstand successfully the demands of O'Neill.
Hugh, who in the family feud with Calvagh had allied himself with O'Neill, now turned round and combined with the English to crush the hereditary enemy of his family; and in 1567 he utterly routed Shane at Letterkenny with the loss of 1300 men, compelling him to seek refuge with the MacDonnells of Antrim, by whom he was treacherously put to death.