Ceallachan (Callahan, Callaghan, Cellachan, Ceallaghan, Cellachain, Ceallachain) of Cashel (Caisal, Caisil), was the 10th century King of the Irish province of Munster (i.e. the southwestern quarter of Ireland) from whom the family names of Callahan and MacCarthy and their variations (e.g. Callaghan, O'Callahan, O'Callaghan, MacCarthaig, etc.) were derived. This website makes available historical sources and written accounts about his life and legacy including the Irish Medieval Saga of Ceallachan of Cashel, the various Irish Annals, and The Circuit of Ireland.
Topics covered in Parts 1, 2, and 3 of the Irish saga Caithrem Ceallachain Caisil, The Victorious Career of Cellachan of Cashel or The Wars Between the Irishmen and the Norsemen in the Middle of the 10th Century. Since most Callahans probably moved to America in the 1840's during the period of the potato famine, and the saga was not translated into English until 1905 (in Norway), most Americans with a Callahan surname probably are unaware that a medieval Irish saga exists about their 10th century ancestor.
PART 1
The list of the kings of Munster before Ceallachan and their causes of death
The oppression of the Irish by the Vikings
Ceallachan's ancestry
Ceallachan prepares to be king by posing as a cleric for a year and a half, secretly reconnoitering the countryside
His mother collects arms and retains soldiers
Cennedig's (Kennedy's) rivalry for the kingship during the election at Glennamain
Ceallachan's mother's speech to the assembly at Glennamain
Cennedig and Donnchad leave the assembly mound
The inauguration of Ceallachan
Ceallachan's call for war and an attack on Limerick
Suilleban (Sullivan) addresses the soldiers
The Battle of Limerick
Ceallachan's combat with Amlaib
Suilleban's combat with Morann
Donnchad's combat with Magnus
Ribordan's combat with Lochlann and the battle inside the town
The poem composed about the Battle of Limerick
The Battle of Cork
The Battle of Sliab Crot
The Battle of Thurles
Ceallachan's address to Donnchad before the Battle of Cashel and the poem
The Battle of Port Lairge (Waterford)
Taking hostages and pledges from the Deisi, Ui-Mic-Caille, and Ui Liathain
The Battle at Muscraige with the Loch Lein Eoganachts
The Battle with Congal in Aes Irrais
The Battle of Glenn Corbraigi
Donnchuan, son of Cennedig, joins Ceallachan to fight Flannabra, king of Ui Conaill and the poem
The Battle of Cromad
The celebration in Cashel of the expulsion of the Norsemen from the towns and fortresses
Demanding taxes from Ossory and the battles with the Leinstermen
PART 2
The Donnchadh, the King of Ireland, agrees to the Viking plot to kill Ceallachan because Ceallachan had not agreed to pay him tribute
Ceallachan wants to go with an army to Dublin but is dissuaded and instead goes with 80 men
Sitric tells his wife, Mor of the plan and because she is secretly in love with Ceallachan she warns him on the road to Dublin
The poem describing the meeting between Mor and Ceallachan
Ceallachan and his men are pursued by the Vikings on foot and by horse
Several of Ceallachan's men fight rear guard actions against the pursuing Vikings
Ceallachan and Donnchadh are captured, and the Vikings exhibit the heads of the slain Irish for identification
Ceallachan's poem lamenting the death of the riders of Munster
Sitric's ransom demands
Ceallachan instructs Aistrechan, son of Ailgisech, what to tell the men of Munster (2 poems)
Ceallachan tells Cennedigh to stay and defend Munster
Aistrechan returns to Munster and describes the situation
Donnchad, the son of Caem, agrees to a rescue expedition and recites Ceallachan's 15 battles
The expedition is organized
Donnchad is made the leader of the expedition
The route of the hosting
Muirchertach son of Airnelach, the king of Cenel Conaill, warns the Vikings to move Ceallachan to Dundalk
The Battle of Armagh
Donnchadh is told that Ceallachan was moved to Dundalk
The army goes to Dundalk and Sitric binds Ceallachan and Donnchuan, the son of Cennetig to the mast
Donnchadh reproaches Sitric (poem)
Ceallachan addresses Donnchadh and sees the approaching Munster fleet (poem)
Duinechad, son of Fiangus, arranges the order of battle
The Battle at Dundalk Harbor
Failbe leaps on to Sitric's ship and cuts Ceallachan loose
PART 3
The Battle on the Viking Ships: The Death of Failbe
Fiangel laments the death of Failbe (poem)
Fiangal pulls Sitric into the sea where they both drown
Seghda and Congal attack but the Viking ships are swamped
The poem about the battle
Conchubar, the king of Ciarraige, kills Ilbrech, son of the king of Lochlann
The Baiscne attack the fleet of the Berserks and kill Lenn Turmun of the Berserks
Donnchuan, son of Ceinneidigh, is freed from the mast
The ships of Munster land and the Vikings leave
Ceallachan laments the death of Failbe
Donnchadh, the son of Caem's poem about the battle
The burial of the nobles in four graves at a church in north Dundalk
Donnchadh, the son of Caem's second poem about the battle
They burn their ships and those of the Vikings and discuss the route home
Ceallachan and Donnchadh urge a route via Dublin
They plunder and burn everything on their way between Dundalk and Dublin
The plot by the women of Dublin fails
The army stays a week in Dublin and Donnchuan. son of Cennedig, takes Bebinn as his wife in Dublin
The Munster army meets the army of Leinster on the route home
They seek revenge on Muirchertach and Donnchadh, son of Flann Sinna, king of Erin and plundered Tara
Ceallachan dies in 952
There is also a good Wikipedia article "Cellachán Caisil"