O'Brien dynasty

The Ó Brian emerged as chiefs of the Dál gCais tribe from the south-west of Ireland and according to historian C. Thomas Cairney, the Dál gCais had come from the tribe of Erainn who were the second wave of Celts to settle in Ireland from about 500 to 100 BC. They were a cohesive set of septs, related by blood, all claiming descent in tradition from a common ancestor of Cas, sixth in descent from Cormac Cas. In the Annals of the Four Masters, the father of Cormac Cas was said to be Oilioll Olum, who was according to tradition King of Munster and King of Leinster in the 3rd century. While founder mythologies were very common in antiquity and the medieval world, such a connection is generally regarded as fanciful and politically motivated in the context of the rise to prominence of the Dalcassians. the O'Rahilly's historical model counts them as ethnically Érainn. The sept split into the Déisi Muman who continued to hold territory in Waterford and Tipperary, while the west Déisi controlled areas either side of the River Shannon. Prehistoric ancestors of the Déisi Tuisceart and Dál gCais may have been a once prominent Érainn people called the Mairtine. It was during this century that the tribe annexed to Munster the area today known as Clare and made it their home. Taken from the weakened Uí Fiachrach Aidhne it had previously been part of Connacht but was renamed Thomond (Tuamhain, meaning North Munster). After gaining influence over other tribes in the area such as the Corcu Mruad and Corcu Baiscinn, the Dalcassians were able to crown Cennétig mac Lorcáin as King of Thomond, he died in 951. The males fit for war were executed at Saingel, while the rest were taken as slaves. The crown of Munster was briefly back in the hands of the Eoghanachta for two years until Brian Boru had thoroughly avenged his brother, with the defeat and slaying of Máel Muad in the Battle of Belach Lechta. ==Rise of Brian Boru==

, High King. The following year Brian came to blows with the Norsemen of Limerick at Scattery Island where a monastery was located. Whilst all parties were Christians, when their king Ivar and his sons took refuge in the monastery, Brian desecrated it and killed them in the sanctuary; the Vikings of Limerick had earlier killed Brian's mother. Following this the Dalcassians came into conflict with those responsible for the death of Mathgamain, the Eoghanachta represented by Donovan and Molloy. A message was sent to Molloy, where Boru's son Murrough would challenge him in single combat; eventually the Battle of Belach Lechta took place where Molloy along with 1200 of his soldiers were slain. Donovan was destroyed together with Aralt, his brother-in-law and Ivar's remaining son, newly elected king of the Danes and Foreigners of Munster, in Donovan's fortress of Cathair Cuan, which Brian razed. With this Brian Boru was now the King of Munster. ==O'Brien dynasty==

Brian's descendants, the Ua Briain provided a further three High Kings of Ireland and exercised supremacy in Munster until Tairrdelbach Ua Conchobair, taking advantage of war between brothers Diarmait and former High-King Muircheartach, invaded Munster and split it in two in the Treaty of Glanmire (1118) granting Thomond to the sons of Diarmait Ua Briain and Desmond to the leading sept of the dispossessed Eoganacht, the Mac Cárthaigh dynasty. After the death of Domnall Mór Ua Briain, a claimant to the Kingship of Munster, they further retreated beyond the Shannon into the area of modern County Clare in the wake of the Norman Invasion. In 1276 King Edward II granted all of Thomond to Thomas de Clare, taking advantage of the feuding between Clann Taidhg and Clann Briain (whom de Clare supported). The de Clares failed in conquering Thomond, and were decisively defeated in the Battle of Dysert O'Dea in 1318, thus the Kingdom of Thomond remained outside of foreign control for a further 200 years. In 1543 Murchadh Carrach Ó Briain agreed to surrender his Gaelic Royalty to King Henry VIII and accepted the titles Earl of Thomond and Baron Inchiquin. At his death in 1551 the Earldom passed to his nephew Donough by special remainder, and the title Baron Inchiquin passed to his male heirs through his son Dermot. The Earldom went extinct at the death of Henry O'Brien, 8th Earl of Thomond; the next heir would have been a descendant of Daniel O'Brien, 3rd Viscount Clare who had been attainded in 1691, so the title became forfeit. However, Charles O'Brien, 6th Viscount Clare, a Jacobite exile used the title Earl of Thomond, as did his son, who died childless in 1774. At the death of James O'Brien, 3rd Marquess of Thomond, the title Baron Inchiquin passed to a distant cousin and descendant of Murrough, Sir Lucius O'Brien, 5th Baronet, and was passed down to his descendants. ==Coat of arms==

The earliest known banner associated with the O’Briens comes from the Dalcassians, the tribal group from which the dynasty descends. This banner is described in the Book of Leinster as featuring the colours "red, purple, gold (yellow), and dung (brown)", though the exact design is not recorded. The Dalcassians held the honour of leading the King of Munster’s army into battle, and their symbolic use of colour predates the formal introduction of Anglo-Norman heraldry to Ireland. Brian Boru, the most famous O’Brien and High King of Ireland, is said to have had two different banners attributed to him. One tradition describes a blue banner displaying an arm holding a sword with a sun. The other features the more recognisable English symbol of three lions. It is argued that the former, with the arm and sword, is more accurate in continuity with the native Irish symbolic system and was used to link Brian’s line with an earlier Munster royal dynasty, the Eóganachta, who used the same symbol. These kings took the throne-name "Magha Nuadhad" ("slave of Nuadu"), referencing the mythological god Nuada Airgetlám of the Tuatha Dé Danann. Nuadu, who lost his arm in battle and was given a magical silver replacement, was disqualified from kingship until his restoration. The emblem of a forearm holding a sword recalls this myth and became a motif of legitimacy and right to rule. However, the arms of the O’Brien dynasty changed dramatically in 1543 when Murrough Ua Briain, the last King of Thomond, surrendered his kingdom to Henry VIII. In exchange, Murrough was created the 1st Earl of Thomond and granted English arms: "gules three lions passant guardant in pale per pale or and argent." This marked a symbolic break from Gaelic sovereignty and an official embrace of English heraldic norms. Although the old arms were formally replaced, the ancient image of the sword-bearing arm survived as a crest, now emerging from clouds to reference the Gaelic motto "Lamh Laidir an Uachtar" ("the strong hand uppermost"). This visual pun maintained a link to the dynasty’s Gaelic past while expressing submission to the Tudor order. In the post-surrender period, the arms were further developed. The quartered arms included new symbols, one being three piles meeting in base; possibly referencing the O’Briens of Arra or adopted from the Anglo-Norman knight Sir Guy Bryan, 1st Baron Bryan due to a similarity in name. Later, the symbol of a pheon (arrowhead) was added to represent loyalty to Sir Henry Sidney, the English Lord Deputy of Ireland. Despite these changes, the core image of the arm and sword persisted as the central crest, preserving the link to both Gaelic kingship and the divine right to rule. ==Family tree==

Key: • = King of Dál gCais • = King of Thomond • = Baron Inchiquin • =Viscount Clare • =Earl of Thomond, Earl of Inchiquin • =Marquess of Thomond {{tree chart|||||HEN||||||CHA||||||WIL||EDW||EDW=Edward2nd Baronet of Leameneh1717-1765|WIL=William3rd Earl of Inchiquin8th Baron of Inchiquin1692–1719|HEN=Henry8th Earl of Thomond1691-1741|CHA={{CSS image crop {{tree chart|||||||||||||CHA||WIL||JAM||LUC|LUC=William4th Earl of Inchiquin9th Baron of Inchiquin1719–1777|JAM=Jamesdied 1771|CHA={{CSS image crop {{tree chart|||||||||||||||||MUR||EDOM||EDW|EDW={{CSS image crop Edward4th Baronet of Leameneh1795-1837|MUR={{CSS image crop {{tree chart|||||||||||||||||WIL||JAM||LUC|LUC=Lucius5th Baronet of Leameneh1837-185513th Baron Inchiquin1855-1872|WIL={{CSS image crop ==Notes==