Editing Brian Boru (section)

== Clashes with the High King ==
[[File:Brian Boru Banner.jpg|thumb|left|Banner reputedly used by Brian<ref>Sir Lee MacMahon, ' Some Celtic Tribal Heraldry and Ancient Arms of Ireland, ' Irish-American Genealogist. The Augustan Society: Torrance, CA. Annual 1979. pp. 256–259.</ref> of which the [[Clare GAA]] colours are based.]]
Having established unchallenged rule over his home [[Munster|Province of Munster]], Brian turned to extending his authority over the neighboring provinces of [[Leinster]] to the east and Connacht to the north-west. By doing so, he came into conflict with High King [[Máel Sechnaill mac Domnaill]] whose power base was the [[Kingdom of Meath|Province of Meath]].

For the next fifteen years, from 982 to 997, High King Máel Sechnaill repeatedly led armies into Leinster and Munster, while Brian, like his father and brother before him, led his naval forces of around three hundred ships<ref name=":2">{{Cite book|last=Duffy|first=Seán|year=2014|title=Brian Boru and the Battle of Clontarf|url=https://books.google.com/books?id=7vH4AwAAQBAJ&q=Fleet|publisher=Gill & Macmillan|isbn=9780717157761|quote=Brian initiated a stunning new undertaking in 988. Again his eyes were on opponents to the north, and again he used his geographical advantage to the full by launching onto the River Shannon at Lough Derg—from his very doorstep—an expeditionary river-fleet of some three hundred vessels, including the Norse fleet of Waterford, and directing their course northwards to Lough Ree.|access-date=5 November 2020|archive-date=25 September 2021|archive-url=https://web.archive.org/web/20210925142817/https://books.google.com/books?id=7vH4AwAAQBAJ&q=Fleet|url-status=live}}</ref> up the Shannon to attack Connacht and Meath on either side of the river. He suffered quite a few reverses in this struggle, but appears to have learned from his setbacks. He developed a military strategy that would serve him well throughout his career: the coordinated use of forces on both land and water, including on rivers and along Ireland's coast. Brian's naval forces, which included contingents supplied by the Hiberno-Norse cities that he brought under his control (particularly [[Waterford]]),<ref name=":2" /> provided both indirect and direct support for his forces on land. Indirect support involved a fleet making a diversionary attack on an enemy in a location far away from where Brian planned to strike with his army. Direct support involved [[Navy|naval forces]] acting as one arm in a [[Pincer movement|strategic pincer]], the army forming the other arm.{{citation needed|date=June 2020}}

The conflict began in 982, when Brian was campaigning against the [[kingdom of Osraige]]. With Munster undefended, Maél Sechnaill attacked the Dál gCáis, destroying the sacred tree of Adair, under which many of the chiefs of the Dál gCáis had been crowned, including Brian's father Cénnetig, his brother Mathgamain and Brian himself. In response, Brian led an army into [[County Westmeath|Westmeath]] where he plundered the land.<ref name=":0">{{Cite web|title=Brian Boru–Irish Biography|url=https://www.libraryireland.com/biography/BrianBoru.php|website=libraryireland|access-date=14 June 2020|archive-date=24 April 2020|archive-url=https://web.archive.org/web/20200424024714/https://www.libraryireland.com/biography/BrianBoru.php|url-status=live}}</ref> Brian's fleet did suffer a setback when a squadron of his fleet attacked [[Connacht]], where they killed a prince of Connacht, Muirgius, who was among the defenders. In retaliation, the Connachtmen attacked the ships, massacring the crews.<ref>{{Cite book|last=Duffy|first=Seán|date=11 October 2013|title=Brian Boru and the Battle of Clontarf|publisher=Gill & Macmillan |url=https://books.google.com/books?id=7vH4AwAAQBAJ&q=Fleet|isbn=9780717157761|quote=A squadron of Brian's 300-strong river-fleet were sent into Connacht after harrying Mide. In an encounter with the defending Connachtmen they killed one of Connacht's princes, Muirgius son of Conchobar; but it was otherwise disastrous for Brian's fleet, whose crews were massacred.|access-date=5 November 2020|archive-date=25 September 2021|archive-url=https://web.archive.org/web/20210925142754/https://books.google.com/books?id=7vH4AwAAQBAJ&q=Fleet|url-status=live}}</ref>{{citation needed|date=April 2022}}

Mael Sechnaill launched a [[counter-offensive]] into Munster and in the ensuing battle he defeated the Dál gCáis, killing around six hundred men, including Brian's uncle. There was a period of relative peace between the two afterwards for about nine years, with Brian continuing to campaign elsewhere as he attempted to expand his power in the south and east.{{citation needed|date=April 2022}}<ref name=":0" />

Then in 993, Brian, now in control of much of Munster and gaining ground in Leinster, and unable to make significant progress against the High King on land{{citation needed|date=April 2022}}, decided to utilise his naval superiority to attack Mael Sechnaill. His fleet sailed up the Shannon and invaded the [[Kingdom of Breifne]], in what is now counties [[County Leitrim|Leitrim]] and [[County Cavan|Cavan]]. In doing this, he put pressure on the High King as he was now open to attack from both north and south.<ref name=":0" />

In 996, Brian finally managed to control the province of [[Leinster]], which may have been what led Máel Sechnaill to reach a compromise with him in the following year.{{citation needed|date=June 2020}} The two kings met at Bleanphottogue, on the banks of [[Lough Ree]] in [[County Fermanagh]], where the agreement was made.<ref>{{Cite book|last=Duffy|first=Seán|title=Brian Boru and the Battle of Clontarf|url=https://books.google.com/books?id=7vH4AwAAQBAJ&q=Bleanphuttoge|publisher=Gill & Macmillan|date=2014|isbn=9780717157761|quote=But Brian came away from Bleanphottogue with an agreement that saw him as the equal to his former lord.|access-date=5 November 2020|archive-date=25 September 2021|archive-url=https://web.archive.org/web/20210925142754/https://books.google.com/books?id=7vH4AwAAQBAJ&q=Bleanphuttoge|url-status=live}}</ref> By recognising Brian's authority over ''[[Leth Moga]],'' that is, the Southern Half, which included the Provinces of Munster and Leinster (and the Hiberno-Norse cities within them), Máel Sechnaill was simply accepting the reality that confronted him and retained control over ''[[Leth Cuinn]]'', that is, the Northern Half, which consisted of the Provinces of Meath, [[Connacht]], and [[Ulster]].{{Citation needed|date=June 2020}}

Precisely because he had submitted to Brian's authority, the king of Leinster was overthrown in 998 and replaced by [[Máel Mórda mac Murchada]]. Given the circumstances under which Máel Mórda had been appointed, it is not surprising that he launched an open rebellion against Brian's authority. With Leinster in rebellion, the kingdoms of both Brian and Mael Sechnaill were threatened, and thus they decided to briefly sideline their own conflict to defeat Leinster.{{citation needed|date=June 2020}}

Brian assembled the forces of the province of Munster and Mael Sechnaill assembled those of Meath, with the intention of laying siege to the [[Kingdom of Dublin|Hiberno-Norse city of Dublin]], which was ruled by Máel Mórda's ally and cousin, [[Sigtrygg Silkbeard]]. Together Máel Mórda and Sigtrygg determined to meet Brian's army in battle rather than risk a [[siege]]. Thus, in 999, the opposing armies fought the [[Battle of Glenmama]]. The [[Irish annals]] all agree that this was a particularly fierce and bloody engagement, although claims that it lasted from morning until midnight, or that the combined Leinster-Dublin force lost 4,000 killed are open to question. In any case, Brian followed up his victory, as he and his brother had in the aftermath of the [[Battle of Sulcoit]] thirty-two years before, by capturing and [[Looting|sacking]] the enemy's city.

Sigtrygg fled the city, seeking support from kings in Ulster, but he was turned away by the Ulaid, leaving Sigtrygg few options but to return to Dublin and submit to Brian.<ref name=":5" /> Once again, Brian opted for reconciliation; he requested that Sigtrygg return and resume his position as ruler of Dublin, giving Sigtrygg the hand of one of his daughters in marriage, just as he had with the [[Eóganachta|Eoganacht]] king, Cian. It may have been on this occasion that Brian married Sigtrygg's mother and Máel Mórda's sister [[Gormflaith]], the former wife of Máel Sechnaill.