Editing Causantín mac Cináeda (section)

== Amlaíb and Ímar ==
Viking activity in northern Britain appears to have peaked during Causantín's reign. Viking armies were led by a small group of men who may have been kinsmen. Among those noted by the Irish annals, the ''Chronicle of the Kings of Alba'' and the ''Anglo-Saxon Chronicle'' are [[Ímar|Ívarr]] — Ímar in Irish sources — who was active from [[Kingdom of East Anglia|East Anglia]] to Ireland, Halfdán — Albdann in Irish, Healfdene in Old English — and [[Amlaíb Conung|Amlaíb]] or Óláfr. As well as these leaders, various others related to them appear in the surviving record.<ref>Downham, Smyth, Woolf</ref>

Viking activity in Britain increased in 865 when the [[Great Heathen Army]], probably a part of the forces which had been active in [[Francia]], landed in East Anglia.<ref>Check Nelson</ref> The following year, having obtained tribute from the East Anglian King [[Edmund the Martyr|Edmund]], the Great Army moved north, seizing [[York]], chief city of the [[Northumbrians]].<ref>Downham, Keynes, Woolf.</ref> The Great Army defeated an attack on York by the two rivals for the Northumbrian throne, [[Osberht]] and [[Ælla of Northumbria|Ælla]], who had put aside their differences in the face of a common enemy. Both would-be kings were killed in the failed assault, probably on 21 March 867. Following this, the leaders of the Great Army are said to have installed one [[Ecgberht I of Northumbria|Ecgberht]] as king of the Northumbrians.<ref>Downham, Higham, Keynes, Ó Corráin, Smyth, Woolf</ref> Their next target was [[Mercia]] where King [[Burgred]], aided by his brother-in-law King [[Æthelred of Wessex]], drove them off.<ref>Keynes ...</ref>

While the kingdoms of East Anglia, [[Mercia]] and Northumbria were under attack, other Viking armies were active in the far north. Amlaíb and [[Auisle]] (Ásl or Auðgísl), said to be his brother, brought an army to [[Fortriu]] and obtained tribute and hostages in 866. Historians disagree whether the army returned to Ireland in 866, 867 or even 869.<ref>Downham, Ó Corráin, Smyth, Woolf, AU 866.1.</ref> Late sources of uncertain reliability state that Auisle was killed by Amlaíb in 867 in a dispute over Amlaíb's wife, the daughter of Cináed. It is unclear whether, if accurate, this woman should be identified as a daughter of [[Cináed mac Ailpín]], and thus Causantín's sister, or as a daughter of [[Cináed mac Conaing]], [[king of Brega]].<ref>Downham, ??, FAA.</ref> While Amlaíb and Auisle were in north Britain, the ''[[Annals of Ulster]]'' record that [[Áed Findliath]], [[High King of Ireland]], took advantage of their absence to destroy the [[longphort]]s along the northern coasts of [[Ireland]].<ref>Byrne? Ó Corráin? AU 866.4</ref> Áed Findliath was married to Causantín's sister Máel Muire. She later married Áed's successor [[Flann Sinna]]. Her death is recorded in 913.<ref>Woolf, AU 913.1, Byrne p. 857, poss. same as Amlaíb's wife.</ref>

In 870, Amlaíb and Ívarr attacked [[Dumbarton Rock]], where the [[River Leven, Dunbartonshire|River Leven]] meets the [[River Clyde]], the chief place of the kingdom of [[Alt Clut]], south-western neighbour of [[Pictland]]. The siege lasted four months before the fortress fell to the Vikings who returned to Ireland with many prisoners, "Angles, Britons and Picts", in 871. Archaeological evidence suggests that [[Dumbarton Rock]] was largely abandoned and that [[Govan]] replaced it as the chief place of the [[kingdom of Strathclyde]], as Alt Clut was later known.<ref>AU 870.6, AU 871.2, Woolf, Downham, Smyth.</ref> King [[Artgal of Alt Clut]] did not long survive these events, being killed "at the instigation" of Causantín son of Cináed two years later. Artgal's son and successor [[Run of Alt Clut|Run]] was married to a sister of Causantín.<ref>AU 872.5, Smyth, Woolf.</ref>

Amlaíb disappears from Irish annals after his return to Ireland in 871. According to the ''Chronicle of the Kings of Alba'', he was killed by Causantín either in 871 or 872 when he returned to Pictland to collect further tribute.<ref>Woolf, Downham.</ref> His ally Ívarr died in 873.<ref>Woolf, Downham, AU 873.3</ref>