'Gaelic Ireland' was the political order that existed in
Ireland prior to the
Norman invasion and that ran in parallel to the subsequent nominal
Lordship of Ireland throughout most of the country until the establishment of the
Kingdom of Ireland. It was ruled as a
elective monarchy, with a
High King nominated from among the kings of the patchwork of kingdoms that made it up.
Political structure

Ireland in 1014 showing the patchwork of kingdoms. Clockwise from the north-east they are: Ulidia, Oriel, Southern Ui Neill (Meath), Leinster, Munster, Connaught, Breifne, and Northern Ui Neill. The cities states of Dubh Linn (Dublin), Wexford, Waterford, Cork and Limerick are also shown.
The Gaelic order in Ireland, rather than a single unified kingdom in the feudal sense, was comprised of a patchwork of kingdoms, which grew and shrunk with the relative powers of their rulers. Since the 8th century these were nominally subservient to the rule of a High King; however, it was not until the eleventh century, with high kingship of Brian Boru, that the office of the high king began to resemble a "national" king in a similar sense to continental Europe. This process has been steadily moving with the title of high kingship passing between a small number of compact families (O Brien of Munster, MacLochlainn of the North, O Connor of Connacht) who intermarried and competed against each other on a national basis. On the eve of the Anglo-Norman incursion of 1169, we find the agglomeration-cum-consolidation process complete and the provincial kingdoms divided and transformed into fiefdoms.
Clan structure and lineage
Lineage was based on the practice of
tanistry whereby a successor was appointed prior to the death of a ruler, rather than based on blood lineage. The clan system formed the basis of polity. Oftentimes, these are thought of as based on kinship, in fact, as Nicholls describes, these would better to thought of as akin to the modern-day corporation. Clans took may shapes and sizes. Their ruling structure, whether ruled by a single lord or a council, changed with according needs and the qualities of their membership. As with a modern corporation, the power of clans grew and shrunk. Once powerful clans could in time reduce in stature and be amalgamated with once smaller ones. How this "merger" would be dealt with would be a matter of negotiation based on the respective power of each party.
Professional classes
The professional classes included hereditary jurists, physicians, harpers and poets and were exempt from military service of their Lord. Although most families of the professional classes practiced only one profession, some exercised more than one, for example the Magraths of Muster were both poets and historians, while the O Duigenans were both historians and musicians. Most at some time turned their hand to the craft of the poet. The official head of each learned profession within a particular territory was titled the ollave (''ollamh''), such as ''ollave in law'' or ''ollave in medicine'', and was appointed by, and served directly, the lord of the territory.
Of these learned classes, the profession of the poet was by far the most ancient. While the learned families in other professions begin to emerge from the 11th century onwards, the class of the poet (''aos dana'' or ''filleadha'') is an extra-ordinary survival from pre-Christian Celtic life. While often his verses were miscalled satires by English observers, "their purpose was magical harm, not ridicule."
[1] Poets formed a different class from mere bards, who were inferior to them, although a bard would often be in the employ of a poet to act as an assistant. Female bards were not unheard of. The delivery of a poem, be it a eulogy, praise or a curse, would often also require the work of a professional reciter (''reacaire''), while a harpist provided accompaniment.
Religion
Since Christianisation c.500 AD, Ireland had essentially rejected the role of the
Papacy in religious matters and paid no tithes to Rome. A division of church and civic life largely existed. With Nicholls reporting that religious teaching having little effect on civic matters such as divorce, marriage, etc. This would in time lead to the eventual ''
Laudabiliter'' which would sanction the Norman (later English) invasion in order to bring the Irish church and polity under papal rule.
The Norman invasion and Gaelic re-conquest

Ireland in 1300, showing lands held by native Irish (green) and lands held by Normans (blue).

Ireland in 1450, showing lands held by native Irish (green), Anglo-Irish (blue) and the English king (red).
Pope
Adrian IV, the only English
pope, had already issued a
Papal Bull in 1155 giving
Henry II of England authority to invade Ireland as a means of curbing Irish refusal to recognize Roman law. Importantly, for later English monarchs, the Bull, ''
Laudabiliter'', maintained papal
suzerainty over the island:
In 1166, after losing the protection of High King
Muirchertach MacLochlainn, the King of
Leinster,
Diarmait Mac Murchada, was forcibly exiled by a confederation of Irish forces under the new High King,
Ruaidri mac Tairrdelbach Ua Conchobair. Fleeing first to
Bristol and then to
Normandy, Diarmait obtained permission from
Henry II of England to use his subjects to regain his kingdom. By the following year, he had obtained these services and in 1169 the main body of Norman,
Welsh and
Flemish forces landed in Ireland and quickly retook Leinster and the cities of
Waterford and
Dublin on behalf of Diarmait. The leader of the Norman force,
Richard de Clare, 2nd Earl of Pembroke, more commonly known as Strongbow, married Diarmait's daughter,
Aoife, and named
tánaiste to the Kingdom of Leinster. This caused consternation to Henry II, who feared the establishment of a rival Norman state in Ireland. Accordingly, he resolved to visit Leinster to establish his authority.
Henry landed with in
1171, proclaiming
Waterford and
Dublin as
Royal Cities. Adrian's successor,
Pope Alexander III, ratified the grant of Ireland to Henry in 1172. The 1175
Treaty of Windsor between Henry and Ruaidhrí maintained Ruaidhrí as High King of Ireland but and codified Henry's control of Leinster, Meath and Waterford. However, with Diarmuid and Strongbow dead, Henry back in England, and Ruaidhrí unable to curb his vassals, the high kingship rapidly lost control of the country. Henry, in 1185, awarded his Ireland to his younger son, John, with the title ''Dominus Hiberniae'', "Lord of Ireland". This kept the newly created title and the Kingdom of England personally and legally separate. However, when John unexpectedly succeeded his brother as King of England in 1199, the Lordship of Ireland fell back into personal union with the Kingdom of England.
By 1261, the weakening of the Anglo-Normans had become manifest following a string of military defeats. In the chaotic situation, local Irish lords won back large amounts of land. A century later, the
Black Death arrived in Ireland. Because most of the English and Norman inhabitants of Ireland lived in towns and villages, the plague hit them far harder than it did the native Irish, who lived in more dispersed rural settlements. After it had passed, Gaelic Irish language and customs came to dominate the country again. The English-controlled area shrunk back to
the Pale, a fortified area around Dublin. Outside the Pale, the
Hiberno-Norman lords adopted the Irish language and customs and siding with the indigenous Irish in political and military conflicts against England, becoming known as the
Old English, and in the words of a contemporary English commentator, became "
more Irish than the Irish themselves."
Although authorities in the Pale grew so worried about the "Gaelicisation" of Ireland and passed special legislation banning those of English descent from speaking the
Irish language, wearing Irish clothes or inter-marrying with the Irish, the government in Dublin had little real authority. By the end of the fifteenth century, central English authority in Ireland had all but disappeared. England's attentions were diverted by its
Wars of the Roses. Around the country, local Gaelic and Gaelicised lords expanded their powers at the expense of the English government in Dublin.
End of the Gaelic order
From 1536,
Henry VIII of England decided to re-conquer Ireland and bring it under crown English control. The Fitzgerald dynasty of
Kildare, who had become the effective rulers of the Lordship of Ireland in the 15th century, had become unreliable allies and Henry resolved to bring Ireland under English government control so the island would not become a base for future rebellions or foreign invasions of England.
In 1541, Henry upgraded Ireland from a lordship to a full
kingdom, partly in response to changing relationships with the papacy, which still had suzerainty over Ireland, following Henry's break with the church. Henry was proclaimed King of Ireland at a meeting of the Irish Parliament that year. This was the first meeting of the Irish Parliament to be attended by the Gaelic Irish chieftains as well as the
Hiberno-Norman aristocracy.
With the technical institutions of government in place, the next step was to extend the control of the Kingdom of Ireland over all of its claimed territory. This took nearly a century, with various English administrations in the process either negotiating or fighting with the independent Irish and Old English lords. The re-conquest was completed during the reigns of
Elizabeth and
James I, after several bloody conflicts.
The flight in to exile in 1607 of
Hugh O'Neill, 2nd Earl of Tyrone and
Rory O'Donnell, 1st Earl of Tyrconnell following their defeat at the
Battle of Kinsale in 1601 and the suppression of their
rebellion in
Ulster in 1603 is seend as the watershed of Gaelic Ireland. It marked the destruction of Ireland's ancient
Gaelic aristocracy following the Tudor re-conquest and cleared the way for the
Plantation of Ulster. After this point, the English authorities in Dublin established real control over Ireland for the first time, bringing a centralised government to the entire island, and successfully disarmed the native lordships.
References
1. Nicholls, K W, 2003, ''Gaelic and Gaelicized Ireland in the Middle Ages'', Lilliput Press: Dublin