But the cursing of Tara was by no means the only misfortune of Diarmaid's reign. His unaccountable hostility to St. Columba involved him in many troubles; and, in addition to these, despite famine and pestilence, the country was afflicted with domestic wars. It is said that his war with Guaire, King of Connaught, was undertaken as a chastisement for an injustice committed by that monarch, who, according to an old chronicle, had deprived a woman, who had vowed herself to a religious life, of a cow, which was her only means of support. It is more probable, however, that the motive was not quite so chivalric, and that extortion of a tribute to which he had no right was the real cause. The high character for probity unanimously attributed to Guaire, makes it extremely unlikely that he should have committed any deliberate act of injustice.
The first great convention of the Irish states, after the abandonment of Tara, was held in Drumceat, in 573, in the reign of Hugh, son of Ainmire. St. Columba and the leading members of the Irish clergy attended. Precedence was given to the saint by the prelates of North Britain, to honour his capacity of apostle or founder of the Church in that country.
Two important subjects were discussed on this occasion, and on each the opinion of St. Columba was accepted as definitive. The first referred to the long-vexed question whether the Scottish colony of Alba should still be considered dependent on the mother country. The saint, foreseeing the annoyances to which a continuance of this dependence must give rise, advised that it should be henceforth respected as an independent state. The second question was one of less importance in the abstract, but far more difficult to settle satisfactorily. The bards, or more probably persons who wished to enjoy their immunities and privileges without submitting to the ancient laws which obliged them to undergo a long and severe course of study before becoming licentiates, if we may use the expression, of that honorable calling, had become so numerous and troublesome, that loud demands were made for their entire suppression. The king, who probably suffered from their insolence as much as any of his subjects, was inclined to comply with the popular wish, but yielded so far to the representations of St. Columba, as merely to diminish their numbers, and place them under stricter rules.