==unique aspect versus other Celts is the reliance on a battle axe in earlier society. La Tene Celts only rarely ever used axes in battle save for a few specific tribes or demi-Celtic cultures, such as Raetians. However, Gaels did practice standard bearing in the same way as La Tene Celts, and probably had similar tactics and traditions based on it. The Gaelic battle axe is not an overly impressive affair; this is probably on purpose. It is a cheap, easy to make weapon that could be widely available. Certain variants could also apparently be thrown. The Gaels also employed many spears with flaring heads, and many early Gaelic swords had 'leaf-shape' blades to increase damage from both thrusts and slashing. Most of these swords were fairly short; longswords were the property of aristocracy and champions more often than regular soldiers. Most soldiers carried a throwing spear, militias carried short javelins, sometimes called 'darts', and at range, slings were preferred over bows, though militias sometimes offered archers, and eventually some Gaels would employ longbowmen adopted from Welsh mercenaries. As an aside, many Gaelic longswords featured an elongated grip to be used in two hands as well as one like a latter period bastard sword, and some Gaelic greatswords precede the mass proliferation of such arms from Germany, though these earlier versions were likely the possessions of individual champions and soldiers.

Armor was usually a simple affair; padded coats, the wealthier might wear boiled leather, and the wealthiest, bronze chest plates or cuirass, rarely mail (though it existed in Ireland, it was rare), or overlapping iron or bronze scales. Helmets were rather like Hallstatt helmets, even into the middle ages. That is, they were usually round, some with decorated cheekguards, and crested with horse hair, or featuring a long plume tail. Like most Celtic helmets, they were modular, so they could be decorated by their owners with such accoutrements. Shields were usually round, the early 'targe' style of shield. However, some early cavalrymen are also depicted with oval or oblong shields.

Full-scale war, and not clan wars, were organized around standard bearers. A regiment of actual soldiers would be given a standard to follow and organize with. Levies, part-time soldiers, and militia, would be assigned to support specific regiments; such as levies of archers following behind, or forming a screen in front, or light cavalry acting as outrunners to harass enemies as they approach or chase down routers. Aristocracy fought alongside the regiments; in early periods, they would probably be among the many charioteers that would be on the field. Later armies, they were usually among the foot soldiers or cavalry, depending on the region and specific nobles. Romans recorded Celts, with standard bearers, as being able to quickly form into lines and reverse a rout incredibly fast; in fact, the Roman reforms incorporated Celtic-style standards because of this. Knowing their own skill, Celts would also feint a retreat, to cause their enemy to disorder and charge them, only to find the routers reorganized and capable of slaughtering the now disorganized attackers. It appears Gaels did this as well. Additionally, they used backpedal tactics; engage in a melee and slowly 'withdraw', bending inward to surround a larger enemy, with supporting regiments and men encircling the foe. All of this relied on standards. When a standard bearer died, a regiment had orders was clearly in their best interests. However, the professional army only trained 4 months out of the year in large scale manuevers, and the other 8 months were spent learning to fight in small scale manuevers for clan wars. Levies only trained 4 months out of the year entirely. This often meant that they were left at disadvantage against a more heavily trained military, but the Gaels were surprisingly capable even so. For many years, even after the Normans declared Ireland a vassal of the king of England, the Gaelic armies were effective enough to make this claim all smoke, and no fire, relegating Norman power in Ireland to the Pale. So valued were Gaelic soldiers in Scotland, that the Norman lords of the lowlands often made exceedingly large sums of payments to convince them to fight in Scotland's wars; the Norman lords practiced feudalism with an Anglo-French-style army, but in the highlands, the ceitherne laws still existed, and the highlanders could not be forced to fight if they didn't want to. Their skill-at-arms, substantial numbers, and their bravery though were extremely valuable.

When the Norse came, the Gaels adapted their military accordingly. That said, there was actually surprisingly little changed. Sword designs were adopted in many places, and mail armor was proliferated more widely, but the Gaels still fought much in the same manner. They began to employ 'Ostmen' to an extent, but they really weren't much different. The Norse in Ireland absorbed a great deal of Gaelic culture, and were ostensibly Gaels themselves, culturally. Gaels did appreciate Norse axe design though, and modified their axes with beards, though, they pointed them the opposite direction, and dropped the 'horse-spike' from the back of many of their axes; a spike used for various tasks, one being to kill a lame horse. The oblong cavalry shield seems to have fallen out of wide use in this time, and cavalrymen began carrying similar targes to what foot soldiers carried. Following the Norse would be the Norman invasions, which would more effectively move the Gaels away from indigenous styles of war.

The most prolific Norse legacy in general Gaelic war though is the creation of the gall-òglaich (Scottish Gaelic) or gall-óglaigh (Irish); the Norse-Gaelic mercenaries who inhabited the Hebrides. They fought and trained in a combination of Gaelic and Norse techniques, and were highly valued; they were hired by everyone in Britain at different times, though most famously the Irish, who used them to replace their decimated heavy infantry core, and, as such, hired many more times of them than anyone else. The French also saw fit to hire them, as they often had a tendency to hire Irish and Scots to help them in their wars, this was a natural progression. Additionally, both the English and French had a habit of hiring Gaelic horsemen, called hobiguir, which became 'hobilar', and were copied by both, though the Gaelic version wore substantially heavier armor.

Other exports and famous pieces include the medieval Irish and Scottish swords; different swords with such unique furnishing that they're some of the only swords in medieval Europe that can be ascribed to use by single nations or cultures. Irish swords, as well as other melee weapons, often featured open rings on the pommel. On any locally designed Irish sword in the middle ages, this meant you could see the end of the tang go through the pommel and cap the end; it also left space to braid scalps of dead enemies; an adaption of the ancient Celtic practice of head hunting. These swords were often of very fine construction and quality, and numerous foreign nobles wished to purchase one, though found it notoriously difficult (though supposedly a few French kings and nobles recieved them as gifts for having been supportive of the Irish in diplomatic talks with England). The Irish swords of this period dropped the earlier Gaelic 'V' guards in most cases, though some persisted in Ulster and Meath, such as on the Irish claíomh mór, an Irish version of the more famous Scottish greatsword. Scottish swords continued to use the more traditional V guards that had been on pre-Norse Gaelic swords, culminating in such pieces as the now famous 'claymore' design. This was an outgrowth of numerous earlier designs, and has become a symbol of Scotland. The name was later applied as well to Scottish and Irish copies of Germanic backswords and baskethilt broadswords, which the Irish and Scots adopted around the same time as they introduced the pistol as a replacement for throwing javelins before charging.