Gaelic warfare was the type of warfare practiced by the Gaelic peoples (the Irish, Scottish, and Manx) in the pre-modern period.
Indigenous Gaelic warfare
Weaponry Irish warfare was for centuries centered on the Ceithearn, or Kern in English (and so pronounced in Gaelic), light skirmishing infantry who harried the enemy with missiles before charging. John Dymmok, serving under Elizabeth I's lord-lieutenant of Ireland, described the kerns as:
"... A kind of footman, slightly armed with a sword, a target (round shield) of wood, or a bow and sheaf of arrows with barbed heads, or else three darts, which they cast with a wonderful facility and nearness..."Fergus Cannan, 'HAGS OF HELL': Late Medieval Irish Kern. History Ireland, Vol. 19, No. 1 (January/February 2011), pp. 14–17
For centuries, the backbone of any Gaelic Irish army was these lightly armed foot soldiers. Ceithearn were usually armed with a spear (gae) or sword (claideamh), long dagger (scian),Sgian-dubh bow (bogha) and a set of javelins, or darts (gá-ín).'HAGS OF HELL': Late Medieval Irish Kern. History Ireland, Vol. 19, No. 1 (January/February 2011), pp. 17
The use of armoured infantry in Gaelic Ireland from the 9th century on came as a counter to the mail-clad Vikings. The arrival of the heavily armoured Norse-Gaelic mercenary Gallowglasses in the early 13th century, was in response to the Norman invasion of Ireland and the Anglo-Normans use of heavily armoured Men-at-arms and Knights.
These adaptations and developments brought regular use of other weapons such as lances, poleaxes like the dane axe, lochaber axe, sparth axe and swords like the arming sword and two-handed swords similar to the Scottish Claymore. Many of the medieval swords found in Ireland today are unlikely to be of native manufacture given many of the pommels and cross-guard decoration is not of Gaelic origin.
By the time of Brian Bóruma and Máel Sechnaill, Irish kings were taking large armies on campaign over long distances and using naval forces in tandem with land forces. From the 11th century on, kings maintained small permanent fighting forces known as lucht tighe "troops of the household", who were often given houses and land on the king's mensal land. These were well-trained and equipped professional soldiers made up of infantry and cavalry.Duffy, Seán, ed. (2005). Medieval Ireland: An Encyclopedia. Routledge. pp. 54–55. ISBN 978-1-135-94824-5.
Aside from Hobelars, who were highly mobile, lightly armoured, cavalry skirmishers and archers, used primarily for scouting and ambushes, the main Gaelic cavalry was usually made up of a king or chieftain and his clan. They usually rode without saddles but wore armour and iron helmets and wielded swords, skenes and long spears or lances.Ó Cléirigh, Cormac (1997). Irish frontier warfare: a fifteenth-century case study (PDF). Archived from the original (PDF) on 30 December 2010. A fully outfitted medieval Irish army would have included light infantry, heavy infantry and mixed cavalry.Flanagan, Marie Therese (1996). "Warfare in Twelfth-Century Ireland". A Military History of Ireland. Cambridge University Press. pp. 52–75.
Gaelic Warfare was anything but stagnant and was adaptive and ever-changing. By the time of the Tudor reconquest of Ireland and the beginning of the end of the Gaelic era, the Irish had adopted continental "pike and shot" formations like those used by the continental armies of the Spanish, Swiss and Germans. With formations consisting of pikemen mixed with musketeers and swordsmen. Indeed, from 1593 to 1601, the Gaelic Irish fought with the most up-to-date methods of warfare, including full reliance on firearms and modern military tactics.G. A. Hayes-McCoy, "Strategy and Tactics in Irish Warfare, 1593–1601." Irish Historical Studies, Vol. 2, No. 7 (Mar. 1941), pp. 255
Gaelic raid culture
The Gaelic Irish preferred hit-and-run tactics and shock tactics like ambushes and raids (the crech), which involved catching the enemy unaware. One of the most common causes of conflict in Gaelic Ireland was cattle raiding. Cattle were the main form of wealth in Gaelic Ireland, as it was in many parts of Europe, as currency had not yet been introduced, and the aim of most wars was the capture of the enemy's cattle. If this worked, the raiders would then seize any valuables (mainly livestock) and potentially valuable hostages, burn the crops, and escape.Ó Cléirigh, Cormac (1997). Irish frontier warfare: a fifteenth-century case study (PDF). Archived from the original (PDF) on 30 December 2010.
Indeed, cattle raiding was a social institution within Gaelic culture and newly crowned kings would carry out raids on traditional rivals upon coronation. The Gaelic term creach rígh, or "king's raid", was used to describe the event, implying it was a customary tradition.
The cattle raid was often called a Táin Bó and was an important aspect of Gaelic literature and culture, with the Táin Bó Cúailnge and Táin Bó Flidhais as important examples. Gaelic warfare was anything but static, as Gaelic soldiers frequently looted or bought the newest and most effective weaponry. Although hit-and-run raiding was the preferred Gaelic tactic in the Middle Ages, there were also pitched battles to settle larger disputes.
Particularly following the arrival of the Vikings from Lochlann, who brought their own style of raiding, warfare and settlements. Over time, these foreign newcomers established themselves, founding their own kingdom in Dublin, establishing a dynastic line and developing a distinct Norse-Gaelic culture of their own.
Armour
It's often stated that for the most part, the Gaelic Irish fought without armour, instead wearing saffron coloured belted tunics called léine (pronounced 'laynuh'), the plural being léinte (pronounced 'layntuh/laynchuh'). According to Gerald of Wales, who wrote propaganda (in the early 12th century), the Gaels preferred not to wear armour, as they deemed it burdensome to wear and one to be "brave and honourable" to fight without it.The Topography of Ireland by Giraldus Cambrensis Archived 17 June 2016 at the Wayback Machine (English translation) Armour was usually a simple affair: the poorest might have worn padded coats, the wealthier might have worn boiled leather armour called cuir bouilli, and the wealthiest might have had access to bronze chest plates, padded textile armour or maybe perhaps mail or scale armours (though they did exist in Ireland, they were quite rare). However, this appears to be all incorrect as the Irish did have heavily armoured knights, as mentioned in the Visio Tnugdali long before the gallowglass came to Ireland. Gallowglass mercenaries of the early 13th century have been depicted as having worn mail tunics and steel burgonet helmets but the overall majority of Gaelic warriors would have been protected only by a small shield. Gaelic shields were usually round, with a spindle-shaped boss, though later the regular iron boss models were introduced by the Anglo-Saxons, Vikings and Normans. A few shields were also oval in shape or square, but most of the native shields were small and round, like bucklers, to better enable agility and a quick escape.
Customs
Clan warfare was an important aspect of life in Gaelic Ireland, especially before the Viking Age, when Vikings brought new forms of technology, culture, warfare and settlements to Ireland.
Before the Viking Age, there was a heavy importance placed on Gaelic clan wars and ritual combat. Another very important aspect of Gaelic ritual warfare at this time was single combat. In order to settle a dispute or merely to measure one's prowess, it was customary to challenge another individual warrior from the other army to ritual single combat to the death, while being cheered on by the opposing hosts.
Champion warfare was an important aspect of Irish mythology, literature, and culture, particularly in the Ulster cycle with Cú Chulainn and the Táin Bó Cúailnge, where the hero from Ulster defeats an entire army from Connacht one by one. Such single combats were common before a pitched battle, and for ritual purposes they tended to occur at river fords.
The spirit and traditions of single combat would live on and manifest themselves in other ways in Modern Gaelic cultures. In Scotland with events like Scottish Wrestling, the Highland Games and Scottish Martial Arts like the dueling of the 18th century, where the victor was determined by who made the first cut. However, this was not always observed, and at times the duel would continue to the death. In Ireland, the spirit of ritual combat has also manifested itself as single combat style sporting events and Irish martial arts such as Irish boxing (Dornálaíocht), Irish wrestling (Barróg), stick fighting (Bataireacht) and scuffling (Coiléar agus Uille).
Urban defense
Many of the towns in Gaelic Ireland had some type of defense in the form of walls or ditches. For most of the Gaelic period, dwellings and buildings were circular with conical thatched roofs.Joyce, Patrick Weston (1906). "Chapter XVI: The House, Construction, Shape, and Size". A Smaller Social History of Ancient Ireland. Library Ireland. Archived from the original on 17 April 2016. Retrieved 14 June 2012. Many towns and dwellings in Gaelic Ireland were often surrounded by a circular rampart called a "ringfort".Connolly, Sean J (2007). "Chapter 2: Late Medieval Ireland: The Irish". Contested island: Ireland 1460–1630. Oxford University Press. pp. 20–24. There were very few nucleated settlements, but after the 5th century, some monasteries became the heart of small "monastic towns",Connolly, Sean J (2007). "Chapter 2: Late Medieval Ireland: The Irish". Contested island: Ireland 1460–1630. Oxford University Press. pp. 20–24.O'Keeffe, Tadhg (1995). Rural settlement and cultural identity in Gaelic Ireland (PDF). Ruralia 1. Archived from the original (PDF) on 2 June 2010. Retrieved 17 November 2010. many of the Irish round towers were built after this period.
Following the Norman invasion of Ireland, the Normans built motte-and-bailey castles in the areas they occupied,Glasscock, Robin Edgar (2008) . "Chapter 8: Land and people, c.1300". In Cosgrove, Art (ed.). A New History of Ireland, Volume II: Medieval Ireland 1169–1534. Oxford University Press. pp. 205–239. doi:10.1093/acprof:oso/9780199539703.003.0009. some of which were converted from ringforts.O'Keeffe, Tadhg (1995). Rural settlement and cultural identity in Gaelic Ireland (PDF). Ruralia 1. Archived from the original (PDF) on 2 June 2010. Retrieved 17 November 2010. Within Gaelic Ireland, many of the areas conquered by Anglo-Normans often had defense walls due to the frontier type of lifestyle. Some had these walls built, assuming that the town had no adequate defense, using only a ditch. The masonry walls in some towns had not been completed due to the economics of the time. While many of the towns often constructed what look to be defensive walls, this can sometimes not be the case. Towns constructed walls and town gates at times as merely a symbol of lordly wealth, or as a physical expression of power; the defensive aspects of some of these walls and gates would become a secondary role.McKeon, Jim (2011). "Urban Defences in Anglo-Norman Ireland: Evidence from South Connacht". Eolas: The Journal of the American Society of Irish Medieval Studies. 5: 146–190. JSTOR 41585270.
By the 12th century, "some mottes, especially in frontier areas, had almost certainly been built by the Gaelic Irish in imitation" of the Normans.Glasscock, Robin Edgar (2008) . "Chapter 8: Land and people, c.1300". In Cosgrove, Art (ed.). A New History of Ireland, Volume II: Medieval Ireland 1169–1534. Oxford University Press. pp. 205–239. doi:10.1093/acprof:oso/9780199539703.003.0009.