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Gaelic British Isles & Ireland

Tribes and States of Ireland


Déisi (Gaels of Ireland)

The island of Ireland sits to the immediate west of the British Isles, at the north-western corner of Europe. In the early days of the historical record it was actually included within the designation of 'British Isles', but the lack of Roman conquest here provided differentiation which eventually removed it from that single classification. It was first settled around 9500 BC, with archaeology providing an uncertain picture of early habitation.

At some point after about 500 BC, Indo-European Celts began to arrive, and perhaps even as early as 2000 BC, providing part of the melting-pot basis for Gaelic Ireland. A legendary high kingship was provided by oral tradition and later writings which began with the Fomóraigh high kings. In the first millennia BC and AD the island remained fully independent of Roman control. Instead the Celto-Irish helped to hasten the end of Roman control over late Roman Britain by constantly raiding the British coastline.

Largely isolated from the chaos which swept Post-Roman Britain during the Anglo-Saxon invasion, Ireland was able to develop its own rich and prominent Christian culture as part of a growing Celtic Church. However, Ireland was never politically united enough to translate its religious and cultural influence into political power, although there were some signs later in the first millennium AD that unity was becoming more likely. Until then, the island was formed from a patchwork of states and tribes, and a constant cycle of raids and warfare.

The Déisi are otherwise shown in written records as Déssi or the unaccented Deisi, pronounced 'day-shee'. This tribe of the County Waterford region in Ireland was apparently settled by the existing Roman authorities in the region of Demetia by AD 382, probably in acknowledgement of a situation which already existed. Their leader of that period, Aed Brosc, was one of his people's key figures. His grandfather, Eochaid Allmuir, had been forced to leave his homeland after a bid for independence failed, and was severely crushed by the Irish high king.

The County Waterford area is interesting in itself. Some archaeological evidence from the island of Lambay, and a second century BC map by Ptolemy, reveal the possibility that some elements of the Brigantes of pre-Roman Prydein had fled there to settle following the conquest of their tribal state by the Romans. It was only towards the end of the first century AD that Brigantine artefacts started to appear in Ireland, and specifically in the Cork/Waterford area, within the later Munster region. Elements of the Deceangli may also have fled to Ireland by the end of the AD 70s to escape Roman rule and retribution.

Now the question arises of whether the Déisi were descendants of these Brigantes refugees. The term 'déisi' is virtually interchangeable with another Old Irish term, 'aithechthúatha', meaning 'rent-paying tribes, vassal communities, tributary peoples'. As a tributary people a bid for power would be natural if they considered themselves powerful and worthy enough.

Clearly this failed in the case of Eochaid Allmuir and the Déisi were forced to escape retribution in Ireland by colonising (or returning to) areas of western Britain. They may also have provided the Irish settlers of Venedotia who were kicked out following the arrival of Cunedda Wledig.

The descendants of Aed Brosc's eldest son, Urb, founded the principality of Brycheiniog between AD 420-450, while his younger son, Triffyn Farfog, married the heiress of the Demetian rulers. Like most Irish royalty, Eochaid claimed descent from Beli Mawr, the Celtic sun god who was also claimed as a second century BC high king of pre-Roman Britain, through his son, Miled. Another branch of the expelled Déisi became the Dál gCais clan of Thomond.

The early Déisi settlers in Demetia were very receptive to the benefits of the Roman way of life, and they gave their children Romano-British names. These were recorded by the early Welsh in Welsh format, and later rulers became completely Welsh in background as Roman influence faded. The Déisi also managed to mangle the name Demetia into Dyfed, although this was during a period in which the British language was rapidly changing towards 'Primitive Welsh', so the change may have been happening anyway.

Irish coracle

(Information by Peter Kessler, with additional information by Edward Dawson, from The Landscape of King Arthur, Geoffrey Ashe, from The Four Branches of the Mabinogi, Will Parker, from Welsh Genealogies AD 300-1400, Peter Bartrum, from A History of Wales, John Davies, 1994, from Welsh Medieval Law, Arthur Wade-Evans, 1909, from the Historia Brittonum (The History of the Britons), Nennius, and De Excidio Brittaniae et Conquestu (On the Ruin of Britain), Gildas (both J A Giles, Ed & Trans, 1841, published as part of Six Old English Chronicles (Henry G Bohn, London, 1848)), from Atlas of British History, G S P Freeman-Grenville (Rex Collins, London, 1979), from Etymological Glossary of Old Welsh, Alexander Falileyev, from An Etymological Dictionary of the Gaelic Language, Alexander MacBain (1982), from Early Irish History and Mythology, T F O'Rahilly, from Ptolemy's Map of Ireland: a Modern Decoding, R Darcy & William Flynn, Journal of the Geographical Society of Ireland, Vol 41 Issue 1 2008, and from External Links: Ancient Welsh Studies, and The History of Ireland (Foras Feasa ar Éirinn - literally the Foundation of Knowledge on Ireland), Seathrún Céitinn (known as Geoffrey Keating, and available via CELT.)

fl c.110 BC

Beli Mawr 'the Great'

High King of Britain. m Don ferch Mathonwy.

Linking the well known figure of Beli Mawr of pre-Roman Britain to the first Déisi leader, Miled (see below) seems to be totally spurious - little more than a faked claim to have inherited the ancient crown of Britain.

A better study of the Déisi pedigree shows that Miled is the mythical Míl Espáine whose Celtic sons lead the exodus from Iberia to southern Ireland where they form the kingdom of Munster (all legendary names here are backed in lilac).

These people are probably Celtiberians, a migration which can be accounted for by taking a look at modern DNA evidence in the Irish. Many of the names to be found in this list are also claimed as early Milesian high kings of Ireland.

This depiction of Celtiberians ambushing Roman soldiers is a glimpse of the bitter Roman battle to control Iberia after the Punic Wars, but just when a group of Celtiberians from the north of Iberia might have migrated to Ireland is unknown, even though it was certainly before this war took place

Miled / Melisius / Galamh


Eremon / Heremon

Son. King of the Milesians in Munster. m Tea.

Irial Faidh / Irial Fáith mac Eremon

Son. King of the Milesians in Munster.

Eithrial / Eithrial mac Irial

Son. King of the Milesians in Munster. Killed.

Eithrial mac Irial is killed at the Battle of Rairiu by Conmáel mac Eibhear. Conmáel is of the Eibhear Finn branch of the clan (effectively, the Finn clan), and the first to claim Munster as his territory (although this contradicts the general Milesian settlement in that region), while Eithrial had been the last of the first generation Gaels to hold the position of high king.

Conmáel fights twenty-five battles against the descendents of Eremon, and is eventually killed by Tigernmas at the Battle of Óenach Macha.

Follain / Follagh


Tigernmas / Tighearnmhas

Son. King of the Milesians in Munster.

Tigernmas mac Faelad fights twenty-seven battles against the Finn clan, almost completely destroying them. But he himself is apparently destroyed along with three quarters of the men of Ireland after worshipping Crom Cruac (Cruach), a god who is related to human sacrifice and who is effectively banished by St Patrick.

St Patrick
This impression of St Patrick in Ireland is one of the less fanciful, and clearly shows the bishop in his later years, towards the end of the fifth century AD

Eanbrotha / Eanbothadh


Smiomghall / Smiorgall


Fiacha Lamhraein

Son. King of the Milesians in Munster. Killed.

The various battles of Fiacha Labhrainne of the Milesian kings include one at sea against the Finn clan, and one against the Érainn (the Iverni, an early mention of this possibly Celtiberian tribe in Munster) at Mag Genainn in County Fermanagh, which results in Loch Erne bursting from the ground.

He also kills Mofebis mac Eochaid in battle. Mofebis' son, Eochaid Mumho, kills him in revenge at the Battle of Sliab Belgatain. Eochaid Mumho is the legendary origin of the name 'Munster', and he fights many more battles against the descendants of Eremon.

Aongus / Óengus Olmucach

Son. King of the Milesians in Munster. Killed.

Maoin / Maen


Rotheachta mac Maen

Son. King of the Milesians in Munster. Killed.

Milesian King Enna Airgtheach is killed by Roitheachtaigh mac Maen at the battle of Raigne. His own death, either twenty-two or twenty-five years later, comes in two versions in the Lebor Gabála Érenn, the first stating that he is killed in single combat in Cruachan by Sedna mac Airtri in defence of his own son, while the second states that he dies of his wounds in Tara.

Whoever the early folk of Ireland were, either in prehistory or mythology, they certainly were not the inventions of later storytellers and oral tradition, the leprechauns

Dein / Deman


Siorna Saoghalach mac Dian

Son. King of the Milesians in Munster. Killed.

Milesian King Sírna mac Dian (Sírna mac Déin or Siorna Saoghalach mac Dian) separates the Ulaid from the authority of the high king and goes to war against its people because they had killed his great-grandmother. The Lebor Gabála Érenn claims that the Ulaid unite with the Fomóraigh (still powerful enough to warrant a military union, it seems).

They engage Sírna at the Battle of Móin Trógaide in Mide, but a plague strikes them, killing the leaders on both sides. According to Seathrún Céitinn and the Annals of the Four Masters, Sírna dies at the hands of Roitheachtaigh mac Roan.

Olioll Olchaoin


Gialcadh / Gaillchadh

Son. King of the Milesians in Munster. Killed.

Nuadat / Nuadhas Fionnfail

Son. King of the Milesians in Munster. Killed.

Aedan Glas / Aedham / Aodhan


Simon Breac / Siomón Brecc

Son. King of the Milesians in Munster. Killed.

Muireadach Bolgach / Murchad

Son. King of the Milesians in Munster. Killed.

Fiacha Tolgrach

Son. King of the Milesians in Munster. Killed.

Duach Ladhrach

Son. King of the Milesians in Munster. Killed.

After having helped Duach Ladhgrach to the high kingship, Lugaid Laigde then kills him and claims the role for himself. He is the son of one of Dáire Doimthech, of the Dáirine, the proto-historical rulers of Munster prior to the rise of the Eóganachta in the seventh century AD.

Neolithic tomb at Poulnabrone in Munster
The Neolithic tomb at Poulnabrone, Ballyvaughan, in County Clare is a portal dolmen which is understood to date from around 2500 BC, with excavations in the 1980s uncovering the bones of fourteen adults and six children

Eochaidh Buidh


Augaine / Ugaine Mor

Son. King of the Milesians in Munster.

Cobthach Caolbhreagh

Son. King of the Milesians in Munster.

Melghe / Melg Molbhthach

Son. King of the Milesians in Munster.

Iaran Gleofathach / Irereo


Conla Caomh / Connla Cáem

Son. King of the Milesians in Munster.

Ailill / Olioll Casfiachlach

Son. King of the Milesians in Munster.

Eochaidh Altleathan

Son. King of the Milesians in Munster.

Aongus Tuirmeach Teamrach

Son. King of the Milesians in Munster.

Enna Aigneach

Son. King of the Milesians in Munster.

Subsequent to Enna there may either be three generations missing from this list, or they have been added later. These are Lava 'the Fierce' Luire (Lorc), son of Enna, and then Beotach (Beothachtach), son of Lava, and finally Blatact, son of Beotach.

Cullyhanna dwelling
This is a reconstruction of a typical Irish dwelling in the Bronze Age, at Cullyhanna in County Armagh, and it is probably safe to assume that the Irish in Demetia initially produced dwellings which were similar

Asaman Eamhna / Essamain

Son of Enna (or Beotach).

Roighean Ruadh






Eochaidh Feidlioch

Son. King of the Milesians in Munster and of Connacht.

Fineamhas / Breas-Nar-Lothar


Lughaidh Sriabhn Dearg

Son. Lewy 'of the Red Circles'.

Crimthann Niadh Nar / Criffan

Son. King of the Milesians in Munster. Died.

Feredach Fionn Feachtnach

Son. King of the Milesians in Munster. Died.

Fiacha Fionn Ola

Son. King of the Milesians in Munster. Overthrown.

AD 43 - 51

Caratacus resists the Roman invasion of Britain, first in the territories of the Cantii and the Catuvellauni, from where he takes shelter with the southern Dobunni. He then moves to the Silures and the Ordovices, before being defeated in battle for the last time.

Initially, the pastoral Brigantes accept the arrival of the Romans who are decimating the tribes in the southern parts of the island. Rather than opposing them or supporting what may be to them distant, possibly 'foreign' tribes (in the form of Belgic groups) they act as a client kingdom.

Map of Britain AD 10
By the end of the first century BC and the start of the first century AD, British politics often came to the attention of Rome, and the borders of the tribal states of the south-east were pretty well known (click or tap on map to view full sized)

72 - 79

Faced with the fact that their northern border is now dominated by a hostile tribe (or confederation) instead of a cooperative client tribe, the Romans invade Brigantes territory under the leadership of new Roman Governor Petillius Cerialis (who had made a notable escape from total defeat during the Boudiccan rebellion in AD 61).

Following a hard campaign, the Brigantes under Venutius are conquered in AD 73, but continued unrest leads to the Brigantine territory being annexed by Rome in AD 79. Some archaeological evidence from the island of Lambay and a second century map by Ptolemy reveal the possibility that some Brigantine elements flee to Ireland and settle there, potentially informing the evolution of the Déisi.

fl 80 - 100

Tuathal Teachtmar / Teachtmhar

Son. High king of Ireland.

Tuathal Teachtmhar, son of Fiacha Finnfolaidh, is the last king mentioned in the original list of high kings as taken from the Lebor Gabála Érenn. Subsequent kings are added by later authors, notably in Foras Feasa ar Éirinn, but these are from Goidelic dynasties which are established by Tuathal.

fl 104 - 113

Felim Rachtmar / Fedlimid Rechtmar

Son. High king of Ireland.

Legendary high king of Ireland, Fedlimid Rechtmar, is the father of future high king, Conn Cétchathach (from AD 116 according to Ireland's mythological timeline). Two other sons are Fiacha Suighe and Eochaid Finn, both of whom are mentioned in medieval sources. Fiacha is also claimed as the ancestor of the Dal Fiachrach Suighe, meaning the 'Seed [descendants] of Fiachra Suighe'.

Queen Cartimandua hands over Caratacus
This print by F Bartolozzi which sits in the British Museum depicts Cartimandua of the Brigantes betraying the movement for British independence in the face of the Roman invasion by handing over a chained Caractacus to the Romans

fl 120s/130s

Fiacha / Fiachu Suighe / Suidhe / Suidge

Son. Brother of Conn Cétchathach of Ireland.

fl c.150s

Cairbre / Cairpre Rigronn mac Fiachach


Corp mac Cairpre


Mes Gegra mac Cuirb


Mes Corp mac Mes Gegra


fl c.250s

Art Corp / Artchorp mac Mes Cuirb

Son. Descended from Fedlimid Rechtmar of Ireland.


According to legend, Cormac mac Airt is high king of Ireland ('Ard Ri na Eireann') during the time of Finn mac Cuill (Fionn mac Cumhaill, or Finn MacCool). He is also one of the country's most popular high kings, being mentioned in many tales and poems and also in the Irish annals, the Annals of the Four Masters. He fights many battles, subduing the Ulaid and Connachta and continuing the ongoing struggle to bring Munster to heel.

In the story The Expulsion of the Déisi, the great-great-great-grandson of legendary high king of Ireland, Fedlimid Rechtmar (AD 104, according to Ireland's mythological timeline), is Art Corb. His four sons are expelled from Tara following a failed bid to take the high kingship.

Cruachan in County Roscommon)
The Bronze Age mound at Cruachan (now Rathcroghan in County Roscommon) served as the royal centre of the most powerful leaders of the Connachta, even during the kingdom's last days in the fifteenth century

Cormac mac Airt is also mentioned in this eighth century text when he is blinded by Óengus Gaíbúaibthech of the Déisi. As no high king can remain in place if he bears a physical blemish, Cormac is replaced by Eochaid Gonnat, although a year later he is killed in battle by Cormac's son, Cairbre Lifechair.

Art Corb's sons each go their own way. The group which is led by Eochaid Allmhuir (Allmhuir meaning 'over-sea') settles in Demetia around the start of the fourth century AD, while another eventually settles amongst the Déisi of southern Munster (the Déisi Muman).

These events have been tied to Scotti (Irish) pirate raids along the length of Britain's western and southern coasts in the fourth and fifth centuries, and to the foundation of the Brito-Irish kingdoms of Dyfed and Brycheiniog. Another branch of the expelled Déisi becomes the Dál gCais clan of Thomond.

fl 244 - 272

Óengus Gaíúaibthech

Of the Déisi. Killed.

During the high kingship of Cairbre Lifechair in Ireland, his sons Fiacha Sraibhtine and Eochaid Doimlen kill Óengus Gaíbúaibthech of the Déisi. In an attempt to heal the breach, Cairbre betroths his daughter, Sgiam Sholais, to a Déisi prince but the fianna (a form of semi-independent warband) demands a tribute of twenty gold bars.

Marloes Sands
The coast of Pembrokeshire, part of the territory of the Demetae and the later kingdom of Dyfed, is a mixture of sandy beaches and daunting rocks (as at Marloes Sands, shown here), but there would have been many places for the Déisi to land and seize some territory

Deciding to cut the fianna down to size, Cairbre gathers a huge army from Connacht, Laigin, and Ulaid, with support from Goll mac Morna and his followers from the fianna itself, while the Déisi and Munster side with the fianna.

Cairbre is victorious at the resultant Battle of Gabhra, but dies in single combat against Oscar, grandson of his own father-in-law, Fionn mac Cumhaill (Finn MacCool). Oscar dies of his own wounds shortly after. The only fianna survivors are Caílte mac Rónáin and Fionn's other son, Oisín.

The subsequent high kings are brothers Fothad Airgthech and Fothad Cairpthech. A year after acceding, one kills the other and the survivor is then killed by Caílte mac Rónáin of the fianna and the followers of Caibre's son, Fiacha Sraibhtine, at the Battle of Ollarba.

fl c.270s

Eochaid Allmuir 'Over-Sea'

Son of Art Corp. Possible first Déisi leader in Demetia.

Corath mac Eochaid



It seems to be Magnus Maximus, the father of Antonius of Demetia, who settles the Irish Déisi within the territory's borders. The act would fit in with a general policy of this period of shoring up late Roman Britain's defences by moving entire groups of people to defend the weaker areas - most notably a group of Romanised Venicones to Venedotia.

Aed Brosc seems to be the Déisi leader who is contacted and invited to settle in Demetia probably in the period between 380-383, although they may already be present from about AD 300.

Magnus Maximus coin
The reverse of this coin issued by Magnus Maximus during his reign as co-emperor shows him standing, holding a laburnum and Victory on a globe

fl 382

Aed Brosc / Ewein Vreisg

Son. Historical leader of the Déisi in Dyfed.

fl c.405

Urb mac Aed

Son. Migrated into the Brycheiniog region.


Anlach, grandson of Urb mac Aed, marries Marchel, whom later Welsh works describe as the 'heiress of Garthmadrun'. The same works give Anlach's father as Cornac or Coronac, who is generally linked to Cormac mac Urb of the Déisi.

Given the calculation that the Déisi may arrive in Dyfed around AD 300, this would give them ample time to become integrated into the regional nobility and for their leading sons to marry the offspring of the surviving Brito-Welsh nobility, hence Anlach's marriage to Marchel. Upon Anlach's death, Garthmadrun becomes Brycheiniog.


Valerian / Triphun mac Aed

Brother of Urb. m Gweldyr of Demetia to form later Dyfed.

The name Triphun is an Irish version of the Latin 'tribune'. Also shown as Trestin, this is clearly a rank rather than a name. His name seems to be Valerian, making him Tribune Valerian, a Romanised Irish king. As the fourth generation of Déisi to have been raised in Britain, the tribe now has roots in the country and has clearly developed a certain degree of reliability and trustworthiness.

Map of Britain AD 450-600
This map of Britain concentrates on British territories and kingdoms which were established during the fourth and fifth centuries AD, as the Saxons and Angles began their settlement of the east coast (click or tap on map to view full sized)

By taking a Roman name, Valerian has become part of the British ruling elite, so much so that he is able to marry Gweldyr, the Romano-British heiress of Demetia, and to become the ruler of what will later be known as Dyfed.

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