The gallowglass were sometimes used in punitive raids of retaliation by the clan chiefs.
"Munster was at this period (1568) in a very disturbed state. Thomas Roe, of Desmond, the brother of the earl, and his cousin, James Fitzmaurice, made a raid into Kerry, which caused the Earl of Clancare to retaliate, by entering Cork and spoiling Lord Roche, who writes, September 14th, from Castletown, 'The Earl of Clancarty, accompanied by M'Donoky, O'Kyve, M'Auly, O'Donocowe More, O'Sullivan More's son, Edmond M'Swyny, and others, with six or seven banners displayed, has taken l,500 kine (cows), burned 7,000 sheep, all his corn, and a great number of men, women, and children.' He therefore desires 'a commission to hurt the said earl'". from ‘History of City & County of Cork’ by C.B.Gibson. (The Earl of Clancare or Clancarty preferred to be called ‘The MacCarthy More’.)
One observer, Richard Stanihurst, says in about 1577:
"The galloglasses were grim of countenance, tall of stature, big of limb, burly of body, well and strongly timbered; feeding on beef, pork, and butter."
The Governor of Ireland, Sir Henry Sidney, on a visit to Cork in 1575, describes the locals who came to pay their respects―
"Lastly, there came to me five brethren, and the sons of two other brethren of one lineage, all captains of galloglasses, called Mac Swynes, who, though I place them last, are of as much consequence as any of the rest; for of such credit and force were they grown into (although they were no lords of lands themselves), as they would make the greatest lords of the province both in fear of them, and glad of their friendship." Letter from Sidney to Privy Council 1575.
It is interesting to note that, 26 years before Kinsale, Mac Swyne gallowglass were paying their respects to the governor. But they had come south 100 years earlier and had probably broken the ties with their distant kinsmen from Donegal who were to fight the English on the side of the Irish earls at Kinsale.
In the late 1500s the struggle for power and territory between the English crown and the Irish earls was reaching its climax. The earls had much success, until the battle of Kinsale, Cork, in 1601. They marched south to face the English. They were supported by the northern gallowglass clans, including the Mac Sweeneys of Donegal, in their efforts to expel the English and reclaim their lands.