The term petty-kingdom is actually a sort of archaic translation of the Old Irish word tuath. In Ireland there was a sort of pyramid of overlordship with provincial kings at the top (there were five of them, one for each of Ireland's historical provinces), regional kings and finally what we call petty-kings - the king of an individual tuath. The tuath was therefore the most basic political unit in early Irish society.

The rulers of these polities did in fact think of themselves as kings despite the fact that an average tuath was only around 50km2 in size. According to Irish law, these kings had very limited powers; they could make peace and war and that was about it (although in reality Irish kings did promulgate and enforce their own laws, and did sometimes impose corporal or capital punishment on criminals). For the Irish, kingship was not symbolized by crowns or thrones but by the adherence to supernatural taboos. Irish kings had to abide by geassa which were supernatural prerogatives and taboos associated with their office; they might forbid him from bathing in certain lakes, from making peace with a neighbouring kingdom, from riding counter-clockwise around their seat of power and so on. Early Irish kingship was very sacral in nature, and an Irish coronation ceremony involved the symbolic marriage between the new king with the feminine personification of his territory, which was likely originally a pagan sovereignty goddess.

Irish kings did not maintain standing armies, but had semi-permanent retinues of noble clients and mercenary troops. Basically, the Irish economy was based around pastoralism and hierarchical relations were established through the renting of cattle. Lords would rent cattle to free-peasants and kings would rent cattle to lords, forming a different kind of relationship. Aristocratic clients were expected to form part of their king's household retinue as part of their contract, while lowborn clients were only obliged to provide processed food products and seasonal labour. Early Irish military forces were therefore small, well-armed horseborne strike-forces made of aristocrats and mercenaries in the service of a king. They would have been engaged in cattle raids and sometimes in large-scale warfare between regional or provincial kings, who held the kings of tuaths in clientship themselves.