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Early History (Also see Early Annalistic References and Early Kings)

The Dál gCais as we know them emerged from the Deisi Becc (Small Deisi, as opposed to the Déisi Mumhan of Waterford), who controlled a strip of land stretching from the Ballyhoura Mountains to the Shannon. They were divided into two groups, An Déis Deiscirt (Southern Deisi) and An Déisi Tuaiscirt (Northern Deisi), who shared a common ancestry. An Déis Deiscirt controlled lands along the Maigue river centred around Bruree and An Déis Tuaiscirt (our group) controlled lands just south of the Shannon centred around Carn Feradaig (Cahernarry), lands they continued to control after their conquest of lands north of the Shannon.(The Dalcassians, by Rev. John Ryan, page 191)

In 629 AD The King of Connacht, Guaire Aidne invaded Munster and was defeated heavily at the Battle of Carn Feradaig, this event being recorded in the Annals. Díoma mac Rónán, a king of the Deisi Tuaiscirt, was said to have been involved in this battle, along with the King of Munster Failbhe Flann. (ALM page 92-94) This event probably marked the Deis Tuaiscirt's expansion into modern County Clare and the formation of the Deis Tuaiscirt polity in the region as only after this point contemporary records note the Déis Tuaiscirt overkings (see Cáin Fhuithirbe 680AD and Cáin Adomnáin 697AD). (Jaski 2014)

However, the "official" history recorded in the Book of Munster would posit this conquest occurred earlier under the Déis Tuaiscirt's ancestor of Lugaid Lámderg. The similarities of of the purported deeds of Lugaid Lámderg and Díoma are striking. Lugaid is mentioned as having effected a conquest of Thomond which began in Carn Feradaig (Lugaid was said to have driven the Connachta "with only boys and hirelings from Carn Feradaig to Ath Lucait"). Lugaid is mentioned as having killed seven kings of the Connachta in seven battles, this is similar to the six Kings of the Connachta said to have perished at Carn Feradaig in 629 AD. (ALM page 94) Thus it seems likely the historical conquests of Díoma have been projected onto Lugaid as part of the formation of a pseudo-history of the early Dál gCais. The most clear purpose of this was to make Brian's own ancestor's (not descended from Díoma) have descent from the early Over-King's of Thomond, which they did not in reality possess.

Along with the expansion of the Déis Tuaiscirt into these Connachta lands on the aftermath of this battle, also likely came the Uí Cormaic (ancestor of O'Hehir and a sept of Uí Fidgente), the Corco Baiscinn (of Munster origin, who first appear in the annals in 722AD fighting the Connachta) and the Eoganacht Aran (ruled in the Aran islands). It was however the Déis Tuaiscirt who clearly benefitted the most from this conquest and so were probably most responsible for it.

Returning to records, in 697 AD, Andelait, son of Díoma is one of eight Munster kings listed as guarantors of the Cáin Adomnáin (list), since the Cáin was only signed by overkings they may have subordinated the Corco Baiscinn and Corco Mruad by this period. They were powerful enough to kill the King of Munster himself in another battle in Carn Feradaig in 713 (see Jaski 2014). In 744 the annals note: "Destruction of Corco Mruad by the Déis" which indicates their power in Thomond was growing. In 765 the death of their king Torpaid is noted in the annals. They enjoyed many privileges from the Eoganacht and were described c. 750AD as "warrior lords" of the King of Munster and were paid off by said king to ensure their loyalty. They may have existed as a buffer state in order to protect Munster from the Connachta. In 834 the Annals report a slaughter inflicted on the Deisí Tuaiscirt by the heathens.

The War Between the Irish and the Foreigners

In 934 AD the Reabachán mac Mothla's death was reported in the Annals. He was reported as Abbot of Tuam Greine, and also as 'King of Dál gCais', the first use of this term. The same year of his death his son was murdered treachorously by Conghalach, son of Lorcáin and Lorcáin was said to succeed Reabachán as King. This event marked a transfer of power in the Dál gCais from Díoma's heirs, who had hitherto provided her kings, to the Uí Toirdhealbhach, a kin group which had been on the ascent in Thomond prior to this. This was a seminal point in our history, and Lorcáin and his heirs would remain in power for over 600 years after this.

They broke free from the suzerainty of the Eoganacht in the mid 900s when Lorcáin's son Cinnéidigh made large strides for the Dál gCais, thriving in the power vacuum left by the disintegrating Eoganacht. This was continued by his son Mathgamhain who seized Cashel and overcame the Eoganacht to become King of Munster. Mathgamain was betrayed and murdered but ultimately avenged by his younger brother Brian Boruma who reclaimed Cashel and killed the conspirators in his brother's murder. Brian also destroyed the vikings of Limerick and killed their leader Ivar.

Brian's ambitions did not end at Munster. He relentlessly attacked the Uí Neill high king Mael Sechnaill who was forced to acknowledge Brian as High King of Ireland in 1002.This was unprecedented as the Uí Neill had held a monopoly on this title for several hundred years (although Brian's relatives had attempted to break this, with several of the Uí Toirdhealbhach dying in battle for Eoganacht king Cormac mac Cuileanáin in Bellaghmoon in 908 against the Uí Neill). He then subdued Ulster and was probably the most powerful and unifying Irish High King, being referred to as "Imperator Scottorum" (Emperor of the Gael), a title not given to any other Irish king, before or after.

On Good Friday 1014 Brian confronted the forces of the King of Leinster who had allied with vikings from Dublin and large viking armies from further afield. The High King's army was victorious at Clontarf, driving the pagan Norse army into the sea and destroying viking power in Ireland permanently, but Brian himself was killed while praying in his tent by the fleeing viking mercenary Brodir, the king was 88 years old. Despite his age Brian wounded the viking warrior, and Brodir was then apprehended and tortured to death by Brian's grand-nephew by having his entrails wrapped around a tree.

Many of Brian's sons died at Clontarf (including his eldest Murchadh and his grandson Toirdhealbhach who drowned chasing the vikings), his eldest living son Donnchadh lead the weary Dalcassian army back to Thomond, facing off the Osraige on the way home.

After this devastation Brian's descendents, the O'Briens would eventually recover and became powerful magnates on a national level, ruling as Kings of Munster and periodically as High King of Ireland (until the Normans invaded in 1169). It is evident that when the Dál gCais expanded across the Shannon into areas formerly held by the Eoganacht (and also westwards into the Corco Mruad and Corco Baiscinn), these areas were colonized by Dalcassian clans.

The Norman Invasion

The Normans invaded Ireland in 1169. In 1174 the powerful King of Munster, Domnall Mór Ua Briain lead a Dalcassian army to confront the Normans at the Battle of Thurles, destroying the large Norman army lead by Strongbow and killing thousands. The Normans were kept from Thomond until Domnall died in 1194 and the disorder caused by the succession of his sons threw his kingdom into disarray and shrunk the O'Briens power into the area of modern County Clare. The Normans would later make further incursions and after the Dalcassian clans ambushed and destroyed the de Clares (cadet branch of the house of Normandy granted Thomond by the English king) in the Battle of Dysert O'Dea in 1318, the O'Briens began to reestablish their position as the dominant magnate in Munster, only rivalled by the Earl of Desmond.

Surrender and Regrant

When Henry VIII began subduing Ireland the leading branch of the O'Briens quickly switched their allegience from the old Gaelic order to the English king, and from essentially 1543, when the King of Thomond was created an English Earl, they became increasingly Anglicized and by 1600 the Earl of Thomond was not even considered Irish any more. This made Thomond's transition to an English client state relatively peaceful, free from the ravages of war and scorched earth tactics suffered in the territories of the Earl of Desmond (who rebelled) and in Ulster where the Gaelic leaders also revolted, these wars of course depopulated these areas and accomodated later plantations.
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