In early 1593, the appointment of an English Sheriff of Fermanagh led to Maguire making the first strikes against the Crown's governance in Ireland.

Maguire held command at the Battle of the Yellow Ford, which resulted in a crucial victory for the Irish confederacy.

He was pardoned in return for an agreement to pay 500 beeves to the crown,[6][5] of which 200 were appropriated by Lord Deputy John Perrot as his perquisite to make Maguire's Gaelic lordship recognised by English law.

On their return towards the river Erne, for unknown reasons Maguire attacked O'Neill's men and killed and wounded many of them.

[4] In October 1591, he bribed Fitzwilliam and Henry Bagenal (Marshal of the Irish Army) with 300 beeves to postpone the appointment of a sheriff.

[5][11][12] In early 1593, Maguire learnt that Lord Deputy Fitzwilliam would be appointing Captain Humphrey Willis as sheriff.

[5] Maguire argued that this violated the deal they had made, and retorted to Fitzwilliam that "your sheriff shall be welcome but let me know his eric [price of compensation for his death] that if my people should cut his head off I may levy it upon the country".

[15] Maguire and O'Donnell wrote letters addressed to Philip II of Spain, requesting urgent reinforcements from the Spanish army.

[15] Encouraged by the Catholic archbishop of Armagh, Edmund MacGauran, but opposed by Tyrone, Maguire invaded Connacht straight away and met with the army of Sir Richard Bingham, president of the province, on mid-summer eve.

The battle of Sciath na Feart took place at Tulsk, in a fog so dense that the sides only realised their proximity when their cavalries were almost upon one another.

[12][citation needed] At the end of 1593, Maguire was wounded in an attempt to prevent Sir Henry Bagenal and Tyrone from crossing the Erne.

[22] Sir Henry Duke sought to relieve the garrison, but Maguire intercepted him at the Arney River and defeated him in the Battle of the Ford of the Biscuits (Beal atha na mBriosgaidh).

[12] During the Irish Nine Years' War (1593–1603), Maguire participated in the Battle of Clontibret in 1595, a significant early defeat for the English, and commanded the cavalry at Mullaghbrack in 1596.

[citation needed] It is assumed that Maguire's death was the reason Tyrone abruptly left Munster and returned to Ulster.

[5][41] The Annals of the Four Masters (c. 1630) describes the reaction to Maguire's death: "[his death caused] a giddiness of spirits and depression of mind in O'Neill and the Irish chiefs in general; and this was no wonder, for he was the bulwark of valour and prowess, the shield of protection and shelter, the tower of support and defence, and the pillar of the hospitality and achievements of the Oirghialla, and of almost all the Irish of his time".

At a banquet attended by the claimants and Tyrone, Hugh Roe O'Donnell proclaimed Cúconnacht as chief, presenting them with a fait accompli.

[1] As part of the Plantation of Ulster, almost all of Fermanagh was confiscated by the Crown and populated by English settlers and lowland Scots,[42] particularly border reivers.

[47] In his 1861 poem Eirinn a' Gul ("Ireland Weeping"), Uilleam Mac Dhunlèibhe, an important figure in 19th century Scottish Gaelic literature, recalled the many stories about his fellow Gaels in Inis Fáil (Ireland) he had heard in the Ceilidh houses of Islay, before that island was emptied by the Highland Clearances.

He then lamented the destruction wreaked upon the Irish people by both famine and similar mass evictions ordered by Anglo-Irish landlords.

He particularly laments the loss of the Chiefs of the Irish clans, who led their clansmen in war and provided "leadership of the old and true Gaelic kind".