There were some 60 Gaelic chieftainships in medieval Ireland, ranging in area from a single barony up to the dominion of The Great
O'Neill, whose authority extended over three to nine counties depending on
his political fortunes. In the north and west, modern Irish counties
approximately reflect territories of the more powerful chieftains in the
16th century, with lesser chiefs holding baronies within these county areas
as vassals of the greater chiefs, following their overlord's 'foreign
policy' and rendering him military service. In border regions between the
spheres of influence of two paramount chiefs, these often competed for the
allegiance of individual sub-chiefs, bribing or terrorising them into
joining one side or the other. English governors similarly competed with
O'Neill for control of chieftains on the borders of the English Pale, such
as O'Reilly, MacMahon and O'Hanlon.
Sub-chieftains collected tribute in money and cattle from their own
subjects for their overlord, keeping back a proportion for themselves.
Fines they imposed for murder or theft might also be shared with the
paramount chief. Sub-chiefs with their nobles were bound to attend a
popular assembly (oireachtas) held by their overlord once or twice a year,
a scene of sporting contests and entertainments for the general public,
which also provided the occasion when the chief held council with his
leading vassals, proclaimed taxes, or even a future war.
Each chieftainship was hereditary within a particular family.
Succession did not necessarily pass to the previous chief's eldest son, but
to the kinsman considered most powerful in terms of wealth and followers,
the choice being made by a council of nobles, including the ruling kindred,
and formally acclaimed by clergy, poets and lesser landowners at the new
chief's inauguration ceremony.
Gaelic society was divided into tenants-at-will, freeholders and
lords. The tenants-at-will were the tillers of the soil and herders of
cattle. They seem to have lived under the jurisdiction of their landlords, without access to the courts of Brehon law, but were also not normally called upon for military service. They probably formed
the majority of the population, but many of the freeholders whose
landownership brought military obligations as well as legal citizenship,
possessed comparatively small farms, representing their share of a larger
family estate. Landownership passed from father to sons, but was
periodically re-divided among cousins when direct heirs failed, by the
senior kinsman (ceann fine). The ceann fine was also responsible for
collecting taxes, debts or fines from his kin-group, unless his authority
was superseded by that of a patron or lord.
Lords based their authority over other freeholders on two types of
vassalage. Humbler clients were bound to biatachas, a 'food-providing
relationship' - rendering food-stuffs and certain labour services to the
lord in return for protection. Nobler clients rendered óglachas or
'military service'. The increasing use of mercenaries by great lords in the
later 16th century distorted this network of personal ties, turning some
into military dictators.