The gallowglasses were elite tribal mercenaries who were a large part of Gaelic armies, both before and after the introduction of gunpowder. They first appeared as organised military regiments in the 13th century, although mercenaries similar to them had been the professional warriors of Highland clans for over a hundred years. Their last appearance in a major European conflict was in the Thirty Years War, which ended in 1648, where many joined the army of the King of Sweden.
The first gallowglasses were Macdougall warriors who could trace their ancestry back to Somerled. In 1259 many were in the service of Prince Aodh Ó Conchobhair of Connaught, which was the dowry of his new bride, a daughter of the King of the Hebrides (this was likely Domhnall mac Raghnaill, whose brother had been killed fighting the English in Ireland).
They had likely been in the service of the Kings of the Hebrides for a long time before this, as they were already a military unit with their own weapons, armour, and fighting style.
After the fall of Clan Macdougall, many other warriors of the clan followed the gallowglasses across the sea rather than fighting in the armies of the Lords of the Isles who did not trust, and were not trusted by, King Robert the Bruce of Scotland, who they had spent a considerable amount of resources on assisting. It is possible that force was used to stop Clan Macdougall from becoming like the MacWilliams of Domhnall Mac Raghnaill's time, by both the Stewarts and the Macdonalds, but there is little evidence for this.
These soldiers married with Norse settlers in Ireland, and, rather than farm and hunt for food, they were provided with food by the local population in return for service to the Irish kings. By the 1300s, other clans also provided gallowglasses, and they were military professionals rather than renegade soldiers.
Training and Equipment
Whilst there was little formal training, many gallowglasses took advantage of the schools back in the Hebrides whilst the weather in Ireland made it impossible for any army to make progress, and thus their services were not required. At these schools they would have learned from experienced professionals how to use their weapons more effectively at the expense of the local tacksman. Those that did not go to these schools would have been those who had acquired enough prestige to be trained at the expense, and often at the court, of the Irish kings.
The skill in weapons that gallowglasses displayed was unmatched in Europe, and there were not many military units in the world who were capable of wielding so many arms and armour. A typical gallowglass would have known how to use a battleaxe, a claymore, a bow, a shillelagh, javelins, darts, and many of the Irish martial arts such as wrestling and boxing. The best gallowglasses would have known how to use longbows, knives, and even early firearms although they generally disdained the use of gunpowder as it could not be employed on rough terrain.
The gallowglass wore mostly chainmail and some leather, although many have also been depicted wearing iron and steel helmets. It many oral stories say that some gallowglasses would have worn robes over their armour, although that may be referring to the professional warriors of clans, such as tacksmen, who were not mercenaries, and who would have worn similar attire.
Each gallowglass would have taken every weapon to a battlefield with him, as well as his food. Their two kerns would have been present, one of which was responsible for the weapons and the other for the supplies. The kerns would have had some basic training and experience in combat, possibly the equivalent of a Highland clansman.
The selection of weapons that gallowglasses wielded meant that they could use most tactics on the battlefield. Their birth gave them knowledge of the tactics of two of the most famous warrior societies - the Celts and the Norse - and their access to mainland Europe made them familiar with the strategies employed by feudal armies. The arrival of the Knights Templar in the Lordship of the Isles after their persecution in the rest of Europe also added to their capabilities.
But the gallowglasses were most often employed to guard the raiding parties and to form the front ranks of an army on the battlefield, although in a charge they would usually throw their javelins before falling back to let the light infantry, or their kerns, take advantage of the gaps in the enemy's lines before they broke them. Their battleaxes were apparently used to scale the walls of small fortifications, and, whilst this is entirely possible, it is unknown whether or not it is just a proud boast that happens to have found itself in someone's family history five hundred years after it was made.
The gallowglasses fought in many wars throughout the centuries, and a few of the major conflicts are included here:
Gaelic Reclamation of Ireland (1261-1536): The initial military defeats of the English in Ireland which weakened their authority were planned and conducted by Hebridean gallowglasses, and gallowglasses continued to assist the Irish kings militarily until the reduction of English authority to the Pale, a small area around Dublin.
First War of Scottish Independence (1296-1328): Many gallowglasses in this war were led by the Lord of the Isles himself, Aonghas Og. They were provided to Robert the Bruce, a Gaelicised Anglo-Norman noble, as the Macdonalds appear to have expected him to be more favourable to Gaelic culture. There were up to five thousand gallowglasses under the command of Aonghas Og during the campaign, and many of these fought at the Battle of Bannockburn.
Second War of Scottish Independence (1333-1357): The gallowglasses fought again, although not under the personal command of Macdonald. Both Wars of Independence were Scottish victories.
Hundred Years War (1337-1453): Most of western Europe was involved, although the gallowglasses fought on most sides, including that of England, as the Lords of the Isles were allied to the Kings of England at the time.
Domhnall MacDomhnuill's Invasion of Scotland (1411): In 1411 the Lord of the Isles claimed the Earldom of Ross on behalf of his wife, and it resulted in the destruction of northeastern Scotland's Anglo-Norman nobility and merchant class although Domhnall failed in his objectives (his son would later inhereit Ross).
Alasdair MacDomhnuill's Invasion of Scotland (1429): Highland chiefs invaded Scotland in retaliation for Alasdair's imprisonment, and as soon as he was released Alasdair provided them with support. They burned Inverness and defeated a royal army at Inverlochy.
Aonghas Og's Rebellion (1490-1493): The last independent Lord of the Isles rebelled against his father for wanting to enter a deal with England which would establish the Gaels as a subservient people in return for half of Scotland in the event of an English invasion. He fought both the loyalist clans and Scotland, defeating both in a brilliant campaign before he was murdered by his Irish harpist.
Reconquest of Ireland (1536-1603): Several conflicts brought Ireland back into English control, and the gallowglasses who'd fought were largely executed after the Desmond Rebellions.
Thirty Years War (1618-1648): The father of modern warfare would have learned many tactics from the gallowglasses during his campaigns in Europe. He is Gustavus Adolphus, King of Sweden, and one of the most famous military figures of the early modern period.
War of the Three Kingdoms (1639-1651): The war across Scotland, England, and Ireland after the Union, and in England known as the English Civil War. In Scotland it was largely a clan war between Clan Donald and Clan Campbell, and it was the same in many areas of northern Ireland. However, the war left a third of Ireland's population slain and most of the population impoverished after the confiscation of their land by Oliver Cromwell's forces.